--- canonical_name: Bulbine natalensis alternate_names: Bulbine latifolia, Rooiwortel, Ibhucu, Ingcelwane, ProLensis canonical_topic: Bulbine natalensis to Improve Testosterone short_topic_lc: bulbine_natalensis_testosterone creation_date: 2026-0723-0008 creator_ai_fullname: Opus 4.8 --- # Bulbine natalensis to Improve Testosterone

Evidence Review created on 07/23/2026 using [AI4L](https://github.com/forever-healthy/AI4L) / Opus 4.8 **Also known as:** Bulbine latifolia, Rooiwortel, Ibhucu, Ingcelwane, ProLensis ## Motivation *Bulbine natalensis* is a succulent herb native to southern Africa, where its stems and roots have long been used in traditional remedies for wounds, skin problems, and as a male aphrodisiac. In recent years it has been sold worldwide as a "natural testosterone booster," most often under the branded extract ProLensis, and marketed to men who want to raise the male sex hormone testosterone without prescription drugs. The interest traces to a small set of experiments in rats, in which stem extract sharply raised testosterone and improved sexual behaviour at low doses, while a higher dose had the opposite effect. The same experiments, however, hinted at strain on the liver and kidneys. To date, only one short human study has been published, and it looked at safety rather than whether the herb actually raises hormone levels in people. This review examines what the available evidence shows about *Bulbine natalensis* and testosterone: the strength and limits of the animal findings, the single human safety study, the proposed biology, the reported risks, and how the herb is sourced and used. It weighs what is known against what remains untested. **[Benefits](#expected-benefits) - [Risks](#potential-risks--side-effects) - [Protocol](#therapeutic-protocol) - [Conclusion](#conclusion)** ## Recommended Reading This section collects high-level, directly relevant reading that introduces *Bulbine natalensis* and its purported effect on testosterone from clinical, expert, and academic angles. * [Short term safety of bulbine natalensis supplementation in healthy men](https://jissn.biomedcentral.com/articles/10.1186/1550-2783-9-S1-P33) - Hofheins et al., 2012 This is the only published human study of the herb. It is a placebo-controlled, double-blind trial in 36 men taking the ProLensis extract for 28 days, and it frames the central gap in the field: the human data address safety, not whether testosterone actually rises. * [Exploring the medicinal potential of Bulbine latifolia (L.f.) Spreng.: a comprehensive review of phytochemicals and therapeutic applications](https://pubmed.ncbi.nlm.nih.gov/42259979/) - Khalil & Bae, 2026 A recent academic narrative review of the plant (now taxonomically classified as *Bulbine latifolia*), summarizing its chemistry, traditional uses, and reported biological activities. It provides the broadest current overview of what is and is not known. * [Is Bulbine Natalensis the Ultimate Natural Testosterone Booster?](https://mikemahler.com/knowledge-center/hormone-optimization/is-bulbine-natalensis-the-ultimate-natural-testosterone-booster/) - Mike Mahler A strength coach and hormone-optimization writer lays out the enthusiast case for the herb, including the widely cited "347% testosterone increase" figure. It is useful for understanding how the animal data are marketed to end users, and where those claims outrun the evidence. * [Bulbine Natalensis Benefits + Side Effects & Reviews](https://supplements.selfdecode.com/blog/bulbine-natalensis/) - Carlos Tello A science-referenced consumer overview that pairs the purported testosterone and libido benefits with the liver, kidney, and lipid concerns from the rodent literature. It is a balanced entry point that foregrounds the safety questions. * [Bulbine Natalensis for Testosterone](https://supplementsinreview.com/testosterone/bulbine-natalensis-testosterone/) - Supplements in Review A structured breakdown of the proposed testosterone mechanisms, typical supplement doses, and the "more is not better" dosing pattern seen in animals. Helpful for seeing how the preclinical dose-response is translated into product recommendations. Note: No qualifying content covering *Bulbine natalensis* in substantial depth was found from the priority experts (Rhonda Patrick, Peter Attia, Andrew Huberman, Chris Kresser, or Life Extension); this reflects the herb's niche status rather than an oversight. ## Grokipedia No dedicated Grokipedia article exists for *Bulbine natalensis* as of the creation date. ## Examine [Bulbine natalensis](https://examine.com/supplements/bulbine-natalensis/) Examine maintains a dedicated, reference-backed page summarizing the herb as a traditional aphrodisiac and testosterone booster, noting that in rat studies it appears potent at raising testosterone but also damages organ function at the same doses. It is the most rigorous independent supplement analysis available for this herb. ## ConsumerLab No ConsumerLab article or product test exists for *Bulbine natalensis* as of the creation date. ## Systematic Reviews No systematic reviews or meta-analyses for *Bulbine natalensis* were found on PubMed as of July 23, 2026. ## Mechanism of Action *Bulbine natalensis* is a botanical extract rather than a single defined molecule, and its testosterone-related effects are attributed to a mixture of constituents. Phytochemical screening of the stem has identified saponins, cardiac glycosides, tannins, alkaloids, and anthraquinones (a class of plant pigment compounds), including the distinctive knipholone-type anthraquinones. The leading proposed mechanism is direct stimulation of steroidogenesis (the body's production of steroid hormones) in the testes. In rats, extract increased both testicular and blood testosterone alongside markers of Leydig-cell activity (the Leydig cells are the testosterone-producing cells of the testes). Because the extract also raised luteinizing hormone (LH, the pituitary signal that instructs the testes to make testosterone) and follicle-stimulating hormone (FSH, the pituitary hormone that governs sperm production), a second proposed route is upstream stimulation of the hypothalamic-pituitary-gonadal axis (HPG axis, the brain-to-testes hormone control loop). A third proposed effect is inhibition of aromatase (the enzyme that converts testosterone into estrogen), inferred from the fall in blood estradiol seen in treated rats. A competing interpretation cautions that these signals are dose-fragile: the same rat work shows that a higher dose reversed the hormonal gains and lowered testosterone, which argues against a simple, linear "more precursor equals more hormone" model and points to a biphasic or even toxic response at the upper end. Human pharmacological properties — absorption, half-life, tissue distribution, and metabolizing enzymes — have not been characterized, so no human pharmacokinetics can be stated with confidence. ## Historical Context & Evolution *Bulbine natalensis* has a long record in traditional southern African medicine, particularly among Zulu and Xhosa communities. Preparations of the stems and roots — often decoctions, infusions, or powdered stem mixed with milk — were used for wound healing, burns, rashes, ringworm, diabetes, vomiting, convulsions, and sexually transmitted infections, and the plant carried a folk reputation as a male aphrodisiac and stamina aid. The shift from traditional aphrodisiac to marketed "testosterone booster" is recent and traces almost entirely to a cluster of rodent studies published between 2008 and 2010 by Yakubu and Afolayan at the University of Fort Hare. Their finding that a low dose of aqueous stem extract sharply raised testosterone, LH, and sexual behaviour in male rats was rapidly picked up by the sports-supplement industry, which commercialized a standardized extract (ProLensis) in the early 2010s. The actual findings of that research are more nuanced than the marketing: the same investigators reported that only low doses helped, that a higher dose suppressed testosterone, and that the extract altered liver and kidney function. Scientific opinion has not converged. The animal signal has never been dismissed as "debunked," but neither has it been confirmed in humans — the only human trial to date examined safety, not efficacy, leaving the central efficacy question genuinely open rather than settled in either direction. ## Expected Benefits All reported benefits below derive from rodent studies or mechanistic inference; none has been confirmed in a human efficacy trial. Benefits are framed for a proactive, health-optimizing adult male reader who would be considering the herb specifically to raise testosterone. ### Low 🟩 #### Increased Testosterone The central claim is that the herb raises testosterone. In male rats, aqueous stem extract increased both testicular and serum testosterone in a dose-dependent, biphasic pattern, with a low-to-moderate dose producing the largest gains and a higher dose blunting or reversing them. The proposed basis is stimulation of Leydig-cell steroidogenesis together with increased LH and FSH. The evidence is graded Low because it rests entirely on short (7–14 day) rodent studies from a single research group, and the one human study measured safety rather than testosterone response — so the human effect is unproven. **Magnitude:** In rats, serum testosterone rose up to roughly 347% above control at the optimal ~50 mg/kg oral dose over 14 days; no human efficacy data exist. #### Enhanced Libido & Sexual Function Consistent with its traditional aphrodisiac use, the extract improved sexual behaviour in male rats. Reported changes included increased mounting, intromission, and ejaculation frequencies, shortened latency to initiate, and enhanced penile reflexes at low doses, paralleling the rise in testosterone and LH. As with the hormone data, the higher dose produced the opposite pattern. This benefit is graded Low: the direction is biologically coherent and reproducible in rats, but there is no human sexual-function trial. **Magnitude:** Rats given 25–50 mg/kg showed increased mount, intromission, and ejaculation frequencies with shortened mount and intromission latencies; not quantified in humans. ### Speculative 🟨 #### Reduced Estrogen (Anti-Estrogenic Effect) Some marketing frames the herb as simultaneously raising testosterone and lowering estrogen. This rests on the observation that treated male rats had significantly lower blood estradiol, interpreted as possible aromatase inhibition. There is no controlled human data; the basis is animal and mechanistic only, so this is graded Speculative. #### Anabolic Support for Lean Mass Because testosterone supports muscle protein synthesis, the herb is promoted for body composition and strength. In rats, extract increased testicular protein, glycogen, and organ-to-body-weight ratios — markers consistent with an anabolic effect on tissue — but no human study has measured lean mass, strength, or performance. If any such effect exists in people it is unproven; the basis is mechanistic and animal-only, so this is graded Speculative. ## Benefit-Modifying Factors * **Baseline testosterone status:** Any perceived benefit is likely to depend on starting hormone levels; a man with clinically low testosterone has more room to respond than one already in the optimal range, though this has not been tested for this herb. * **Aromatase activity (CYP19A1):** Individual differences in the aromatase enzyme, which converts testosterone to estrogen, could influence how much of any testosterone gain is offset by conversion to estrogen and thus the net benefit. * **Sex-based differences:** All testosterone and libido benefits were demonstrated in male rats. In female rats, low doses did not alter reproductive parameters, so the intended benefit is inherently male-specific. * **Age-related considerations:** Because testosterone declines gradually with age, older men within the target audience may in principle be more motivated to respond, but the rodent studies used young adult animals, so age-specific human effects are unknown. * **Pre-existing health conditions:** Underlying hormonal, liver, or kidney conditions could blunt benefit or shift the risk-benefit balance unfavourably; the extract's organ effects make baseline organ health particularly relevant. ## Potential Risks & Side Effects Risks below are drawn from rodent toxicology, human liver-cell interaction studies, and the single 28-day human safety trial. They are framed for a health-aware adult who would be self-administering an unregulated botanical. ### Medium 🟥 🟥 #### Liver Toxicity ⚠️ Conflicted The most consistently raised concern is hepatic strain. In rats, stem extract at the same doses that boosted testosterone raised liver enzymes — including alanine aminotransferase (ALT) and aspartate aminotransferase (AST), which leak from damaged liver cells, plus alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) — and produced mild architectural distortion of the liver lobules. The single human trial, by contrast, found no clinically meaningful liver changes over 28 days, with only a marginal rise in ALP that stayed within the normal range. The evidence is directly conflicted: a clear animal toxicity signal versus a reassuring but short and small human safety study, which is why the risk is graded Medium rather than High and flagged as conflicted. **Magnitude:** In rats, liver function markers shifted by roughly 39% with mild tissue distortion at 25–100 mg/kg; the 28-day human trial found only a ~3% rise in ALP, within normal limits. ### Low 🟥 #### Kidney (Renal) Toxicity The same rodent work reported effects on the kidney, including altered kidney function indices and distortion of the renal tubules, described by the authors as evidence of selective toxicity. The human safety trial showed only a small decrease in creatinine (a kidney waste marker) that remained within the normal range. Graded Low because the concern rests on animal histology at doses that may not translate to human intakes, without corroborating human harm. **Magnitude:** Rat kidney indices shifted by roughly 21% with tubular distortion; the human trial showed a ~7% fall in creatinine, within the normal range. #### Adverse Changes in Blood Lipids In rats, two weeks of extract raised total cholesterol and triglycerides, lowered high-density lipoprotein (HDL, the "good" cholesterol), and increased a calculated atherogenic index — a pattern the authors warned could predispose to atherosclerosis with repeated use. This has not been evaluated in humans. Graded Low as an animal-only signal relevant to a cardiovascular-conscious audience. **Magnitude:** Rats showed increased total cholesterol and triglycerides with reduced HDL and a higher atherogenic index over 14 days; not quantified in humans. #### Herb–Drug Interactions Human liver-cell studies show the extract and its knipholone constituents activate the pregnane X receptor (PXR, a cellular switch that ramps up drug-metabolizing enzymes) and modulate several cytochrome P450 enzymes — inducing cytochrome P450 3A4 (CYP3A4, the enzyme that metabolizes a large share of prescription drugs) and CYP2C9 while also inhibiting CYP2C9, and affecting CYP1A2, CYP2B6, and the drug-efflux pump P-glycoprotein (P-gp). This creates a plausible route to altered levels of co-administered medications. Graded Low because the data are in vitro; clinical interaction magnitude in people has not been established. **Magnitude:** In human liver-cell assays, extract raised CYP3A4 and CYP2C9 activity several-fold and inhibited CYP2C9 catalytic activity; the clinical effect size in humans is not established. ### Speculative 🟨 #### Rebound Testosterone Suppression A recurring enthusiast and rodent observation is that benefit reverses at higher doses or, anecdotally, with prolonged use: rats given the high dose had lower testosterone and progesterone, and user reports describe an initial surge followed by a drop below baseline. A biphasic effect on the HPG axis is plausible but unproven; the basis is animal high-dose data and uncontrolled anecdote only. #### Altered White Blood Cell Counts Rat hematology showed an increase in total white blood cell count and shifts in several cell types after two weeks, which the authors described as a localized systemic toxicity signal. Whether this occurs in humans is untested; the basis is a single animal study. ## Risk-Modifying Factors * **CYP2C9 and other P450 variants:** People carrying reduced-function variants of drug-metabolizing enzymes such as CYP2C9 could experience larger or less predictable interactions when the herb is combined with substrate medications (for example, blood thinners). * **Baseline liver and kidney biomarkers:** Elevated baseline liver enzymes or reduced kidney filtration would amplify the organ-strain concerns; a normal baseline panel is the relevant reference point. * **Sex-based differences:** Toxicology was conducted mainly in male rats; in female rats, low doses appeared reproductively "safe," but the high dose increased fetal resorption, making use during pregnancy a distinct and serious concern for women. * **Pre-existing health conditions:** Existing liver disease, kidney disease, dyslipidemia, or hormone-sensitive conditions could each worsen the risk profile. * **Age-related considerations:** Older adults, who more often take multiple prescription medications and have reduced hepatic and renal reserve, are more exposed to both the interaction and organ-strain risks. ## Key Interactions & Contraindications * **Prescription drug interactions:** Because the extract modulates CYP3A4 and CYP2C9, it may alter levels of a wide range of prescription drugs, including CYP3A4 substrates (statins such as simvastatin, calcium-channel blockers, many benzodiazepines) and CYP2C9 substrates (warfarin, phenytoin, several NSAIDs (non-steroidal anti-inflammatory drugs, common painkillers such as ibuprofen)). Severity: caution to potentially serious; consequence: unpredictable loss of efficacy or increased toxicity of the co-administered drug. Mitigation: avoid combining with narrow-therapeutic-index drugs, or monitor drug levels/effect closely. * **Over-the-counter medication interactions:** Concurrent use with hepatically metabolized OTC agents such as acetaminophen (paracetamol) or high-dose NSAIDs could add to liver strain. Severity: caution; consequence: additive hepatic stress. Mitigation: limit concurrent hepatotoxic OTC use and separate dosing where possible. * **Supplement interactions:** Combining with other CYP-active botanicals (for example, St. John's wort) or with other hepatically processed supplements may compound interaction and liver-load effects. Severity: caution; consequence: altered supplement/drug levels. Mitigation: avoid stacking multiple enzyme-active botanicals. * **Additive (same-direction) supplements:** Other purported testosterone or aromatase-modulating supplements (e.g., *Tribulus terrestris*, *Fadogia agrestis*, tongkat ali) may have additive hormonal effects; there is no evidence such stacks are safe or effective. Severity: caution; consequence: unpredictable additive hormonal shifts. Mitigation: avoid combining unvalidated hormonal botanicals. * **Other intervention interactions:** Alcohol and other hepatotoxins would be expected to compound the liver signal. Severity: caution; consequence: increased hepatic injury risk. Mitigation: minimize alcohol during use. * **Populations who should avoid this intervention:** Women who are pregnant or breastfeeding (high-dose animal data show increased fetal resorption); anyone with pre-existing liver disease (e.g., transaminases above the upper limit of normal) or significant kidney impairment (e.g., estimated glomerular filtration rate (eGFR, a measure of kidney filtration capacity) below 60 mL/min/1.73 m²); people with hormone-sensitive cancers; and anyone taking narrow-therapeutic-index CYP3A4 or CYP2C9 substrate drugs. ## Risk Mitigation Strategies * **Baseline and follow-up organ panels:** Because the primary concern is liver and kidney strain, obtain a liver enzyme panel (ALT, AST, ALP, GGT) and a kidney panel (creatinine, eGFR) before starting and again after 4 weeks, discontinuing if liver enzymes rise above the normal range — this directly mitigates the hepatic and renal toxicity risks. * **Conservative, non-escalating dosing:** Given the biphasic animal pattern where a higher dose reversed benefit and increased harm, keep to the low end used in the human safety study (around 650 mg/day) and avoid the "more is better" approach — this mitigates both rebound testosterone suppression and organ toxicity. * **Time-limited use with cycling:** Limit continuous use to short blocks (e.g., 4–8 weeks) rather than open-ended daily intake to reduce cumulative organ exposure — this mitigates cumulative hepatic, renal, and lipid effects. * **Medication and interaction screening:** Review all prescription and OTC drugs for CYP3A4/CYP2C9 involvement before use and avoid combining with narrow-therapeutic-index agents such as warfarin — this mitigates the herb–drug interaction risk. * **Lipid monitoring for cardiovascular-aware users:** Check a fasting lipid panel at baseline and after a cycle, given the adverse lipid shifts seen in animals — this mitigates the dyslipidemia risk. ## Therapeutic Protocol * **Standard protocol:** There is no clinically validated human protocol. The only human study used the ProLensis extract at 650 mg/day, taken as 325 mg in the morning and 325 mg roughly six hours later for 28 days; commercial products commonly follow a similar 325–650 mg/day range. * **Dose ceiling and biphasic response:** Leading enthusiast practitioners emphasize that higher is not better, echoing the rodent finding that a doubled dose reversed the testosterone gain; protocols therefore deliberately cap the dose rather than titrate upward. * **Best time of day:** No human timing data exist. The safety trial split the dose morning and afternoon; taking it with food may reduce gastrointestinal upset. * **Half-life:** The human half-life of the active constituents has not been characterized, which is one reason split dosing is used empirically rather than by design. * **Single vs. split dosing:** Because the half-life is unknown, the split (twice-daily) schedule from the human trial is the most defensible default. * **Genetic considerations:** Variants in CYP-family enzymes (e.g., CYP2C9) and in aromatase (CYP19A1) could in theory influence both interaction risk and the estrogen-conversion side of any response, though no pharmacogenetic dosing guidance exists. * **Sex-based differences:** The protocol is intended for men; the hormonal rationale does not apply to women, for whom high-dose animal data raise reproductive-safety concerns. * **Age-related considerations:** Older men with reduced hepatic and renal reserve should be especially conservative given the organ-strain signal. * **Baseline biomarkers:** Baseline total and free testosterone, estradiol, and liver/kidney panels help define whether there is room to benefit and a safe starting point. * **Pre-existing conditions:** Liver disease, kidney disease, or hormone-sensitive conditions argue against use regardless of dose. ## Discontinuation & Cycling * **Short-term rather than lifelong:** Nothing in the evidence supports open-ended daily use; the organ-strain and biphasic-response signals argue for short, time-limited use rather than a permanent regimen. * **Withdrawal effects:** No formal withdrawal syndrome has been documented, but anecdotal reports of a testosterone "crash" below baseline after stopping suggest the possibility of a temporary dip in the body's own production. * **Tapering:** No tapering protocol has been studied; because doses are already low, abrupt discontinuation is the norm, with monitoring of hormones if a rebound dip is suspected. * **Cycling:** Cycling — for example, 4–8 weeks on followed by an equal or longer break — is commonly recommended by users both to limit cumulative organ exposure and to counter any tolerance or rebound, though no controlled data confirm a cycling benefit. * **Post-use monitoring:** A repeat liver panel and testosterone measurement after a cycle helps confirm that organ markers and hormones have returned to baseline. ## Sourcing and Quality * **Extract identity (ProLensis):** The only extract tested in humans is the branded ProLensis stem extract; products specifying this or an equivalently characterized stem extract are preferable to generic "*Bulbine natalensis*" powders of unknown preparation. * **Species and part verification:** The genus is taxonomically confused (the plant is now often classified as *Bulbine latifolia*, and related species such as *Bulbine frutescens* are sold), and the testosterone data are specific to the stem; look for products that name the species and plant part explicitly. * **Standardization of anthraquinones:** Analytical work has shown that anthraquinone content varies substantially across commercial supplements, so third-party assays quantifying knipholone-type anthraquinones add confidence in potency and consistency. * **Third-party testing:** Because botanicals are vulnerable to adulteration and heavy-metal or microbial contamination, independent third-party testing (identity, potency, contaminants) is the key quality signal. * **Reputable suppliers:** Prefer brands that publish certificates of analysis and use a named, characterized extract; avoid unbranded bulk powders with no potency or purity documentation. ## Practical Considerations * **Time to effect:** Unknown in humans. Rodent hormonal changes appeared within 1–7 days, and marketing often implies a similarly fast response, but no human onset data exist. * **Common pitfalls:** The most common mistakes are dose escalation (chasing bigger effects despite the animal evidence that higher doses backfire), stacking with other unvalidated hormonal botanicals, ignoring liver monitoring, and assuming rat percentage gains translate directly to humans. * **Regulatory status:** In the United States it is sold as a dietary supplement, not an approved drug; it is not evaluated by the FDA for testosterone claims, and quality and labeling accuracy are not guaranteed. * **Cost and accessibility:** It is inexpensive and widely available online; accessibility is not a limiting factor, which makes the safety and efficacy questions the more important considerations. ## Interaction with Foundational Habits * **Sleep:** Direction — largely unknown. There is no evidence the herb improves or disrupts sleep directly; because healthy testosterone depends heavily on adequate sleep, poor sleep would likely blunt any hormonal benefit far more than the herb could add. Practical point: prioritize sleep as the higher-leverage lever. * **Nutrition:** Direction — indirect/potentiating for the goal, with a possible drawback. Adequate dietary fat and micronutrients (zinc, vitamin D) support endogenous testosterone, so the herb sits within a broader nutritional context; however, the adverse lipid shifts seen in animals argue for pairing use with a heart-healthy diet and taking doses with food to limit gastrointestinal upset. * **Exercise:** Direction — potentially additive for the stated aim. Resistance training reliably raises acute testosterone and supports lean mass, the same outcomes the herb is marketed for, so any real effect would overlap with — and be dwarfed by — consistent strength training. Practical point: exercise is the primary driver; the herb is at best a minor adjunct. * **Stress management:** Direction — indirect. Chronic stress and elevated cortisol suppress testosterone, so unmanaged stress would work against the goal; there is no evidence the herb modifies the stress response itself. Practical point: stress reduction addresses a root driver the herb does not touch. ## Monitoring Protocol & Defining Success Baseline testing before starting is advisable given the organ-strain signal and the goal of tracking a hormonal response. At minimum, establish baseline hormone and liver/kidney values so that any change can be interpreted against the individual's own starting point. Ongoing monitoring cadence: re-check the liver and kidney panels at about 4 weeks (the duration of the only human trial), reassess hormones after a full cycle, and repeat every 3–6 months if use continues, stopping earlier if liver enzymes rise. | Biomarker | Optimal Functional Range | Why Measure It? | Context/Notes | | --------- | ------------------------ | --------------- | ------------- | | Total testosterone | ~500–900 ng/dL (men) | Primary target outcome | Draw in the morning; conventional lab "normal" starts near 264 ng/dL, lower than the functional target | | Free testosterone | ~15–25 pg/mL (men) | The biologically active fraction | Interpret with SHBG (sex hormone-binding globulin, the protein that binds testosterone in blood) | | Estradiol | ~20–30 pg/mL (men) | Tracks conversion of testosterone to estrogen | Use a sensitive assay; the herb is claimed to lower it | | Luteinizing hormone (LH) | ~2–8 mIU/mL | Shows whether any effect is central or testicular | Paired with FSH clarifies the site of action | | ALT / AST | ~10–30 U/L | Detects liver-cell strain | Conventional upper limits (~40–55 U/L) are higher than the functional target; fasting preferred | | ALP / GGT | ALP ~40–100 U/L; GGT <30 U/L | Sensitive liver signals seen in animal and human data | GGT is a sensitive marker of hepatic and alcohol-related stress | | Creatinine / eGFR | Creatinine ~0.8–1.1 mg/dL; eGFR >90 | Detects kidney strain | Hydration and muscle mass affect creatinine; pair the two | | Fasting lipid panel | HDL >50 mg/dL; triglycerides <100 mg/dL | Captures the adverse lipid shift seen in animals | Requires 9–12 h fast; interpret alongside baseline | Qualitative markers to track alongside labs: * **Libido and sexual function:** subjective drive, erectile quality, and frequency of spontaneous interest. * **Energy and mood:** daytime energy, motivation, and any irritability or aggression (reported anecdotally at higher exposure). * **Physical signs:** any acne, unusual fatigue, right-upper-quadrant discomfort, or dark urine that could signal liver strain. * **Strength and recovery:** training performance and recovery as a practical proxy for any anabolic effect. ## Emerging Research * **No registered clinical trials:** A search of ClinicalTrials.gov returned no registered interventional or observational studies of *Bulbine natalensis* for testosterone or any other endpoint as of the creation date, so there are no ongoing trials to report with NCT identifiers. * **Need for human efficacy trials:** The decisive open question — whether the herb raises testosterone in men — has never been tested in a controlled human trial; the existing human report ([Hofheins et al., 2012](https://jissn.biomedcentral.com/articles/10.1186/1550-2783-9-S1-P33)) explicitly framed itself as a first-step safety study and called for follow-on efficacy work. A properly powered randomized controlled trial (RCT) could either substantiate or overturn the marketing claims. * **Extract standardization and active compounds:** Analytical chemistry work ([Bae et al., 2020](https://pubmed.ncbi.nlm.nih.gov/31766069/)) developed methods to quantify the anthraquinones in extracts and supplements, a prerequisite for reproducible dosing; identifying which constituents (if any) drive the hormonal effect is an active and clarifying direction. * **Herb–drug interaction risk:** In vitro human studies ([Husain et al., 2021](https://pubmed.ncbi.nlm.nih.gov/33321412/)) flag CYP3A4/CYP2C9-mediated interaction potential and call for translational human studies; this line of work could weaken the case for the herb if clinically meaningful interactions are confirmed. * **Direction of evidence:** Future findings could cut either way — a positive human efficacy trial would strengthen the case, while confirmation of the animal hepatotoxicity and interaction signals in people would weaken it — so both strengthening and weakening evidence are genuinely anticipated. ## Conclusion *Bulbine natalensis* is a southern African herb, traditionally used as a male aphrodisiac and now widely sold as a natural testosterone booster. The enthusiasm rests almost entirely on a small group of short rodent studies in which low doses of stem extract sharply raised testosterone and improved sexual behaviour, while a higher dose reversed those gains. Those same animal studies also pointed to strain on the liver and kidneys and unfavourable shifts in blood fats, and laboratory work suggests the herb could interfere with how the body processes common medications. The single human study to date looked only at short-term safety, not at whether the herb actually raises hormone levels in people, and it found no clear harm over four weeks. This leaves a genuine gap: the headline testosterone claims come from rats, not men, and the organ concerns come from the same rat doses that produced the benefits. The overall evidence base is thin, comes largely from one research group, and has not been confirmed in humans. What can be said is that the animal signal for raising testosterone is real but unproven in people, the safety picture is reassuring only over a short window, and the biology appears dose-sensitive, with more not being better. The most notable feature of this herb is how little human evidence supports a very confident marketing story. **[Top](#top) - [Benefits](#expected-benefits) - [Risks](#potential-risks--side-effects) - [Protocol](#therapeutic-protocol)**