Bulbine natalensis to Improve Testosterone - Quick Reference Sheet
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Bulbine natalensis to Improve Testosterone

Created on 09/14/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 5 – Audit

A southern African herb sold as an oral supplement said to raise testosterone. The claim rests on rat work from one university group: low doses raised hormone levels, a higher dose reversed the effect. Nothing comparable has been measured in people. Liver and kidney chemistry shifted at the same doses, and several products contain none of its marker compounds. (Full Review)

Protocol

The trial-anchored regimen
650 mg daily, 28 days
325 mg of a standardised extract in the morning and 325 mg six hours later. The only human exposure ever run.
The allometric-scaling regimen
~8 mg/kg
The rat optimum of 50 mg/kg converted by body surface area — about 550 mg for a 150 lb adult.
Single versus split dosing
Split, morning and early afternoon
Two doses six hours apart, following the human trial; morning dosing aligns with the natural testosterone peak.
Time to effect
Testosterone
Unknown in humans
The only human trial ran 28 days without measuring any efficacy endpoint, so no human onset interval can be quoted.
Rodent hormone change
1–7 days
Rodent hormone changes appeared within 1–7 days of dosing; the rodent studies ran 1–14 days.
Durable hormone change
12 weeks
The earliest point at which a durable hormone change would be credible.

Benefits

Contraindications
  • Testosterone replacement therapy and hCG
  • Alanine or aspartate aminotransferase above 3× the upper limit of normal, or any active hepatitis
  • Cirrhosis of Child-Pugh Class B or C
  • Estimated glomerular filtration rate below 60 mL/min/1.73 m²
  • Known or suspected hormone-sensitive prostate cancer, or prostate-specific antigen above 4 ng/mL
  • Men actively trying to conceive
  • Anyone on warfarin, a diagnosed bleeding disorder, or within 14 days of scheduled surgery
  • Pregnancy and breastfeeding
  • Anyone under 18, and women
    •
Key Interactions
  • CYP3A4 substrates (tacrolimus, ciclosporin, simvastatin, apixaban, rivaroxaban)
  • CYP2C9 substrates (warfarin, phenytoin, glimepiride, celecoxib)
  • CYP1A2 and CYP2B6 substrates (theophylline, clozapine, olanzapine, bupropion, efavirenz)
  • P-glycoprotein substrates (digoxin, dabigatran)
  • Over-the-counter paracetamol, ibuprofen and naproxen
  • Anthraquinone-bearing supplements (senna, cascara, aloe latex, rhubarb root)
  • Hepatically stressful supplements (green tea extract, kava, high-dose niacin, ashwagandha)
  • Antiplatelet and anticoagulant supplements (fish oil, ginkgo, garlic extract, high-dose vitamin E)
  • Other androgenic or aromatase-directed supplements (Tribulus terrestris, Eurycoma longifolia, DHEA, boron)
    •

Risk & Side Effects

  • Medium: Liver and kidney marker disturbance
    •
  • Low: Unreliable dose delivered by commercial products
    •
  • Speculative: Herb-drug interaction via drug-metabolising enzymes; unfavourable blood lipid shift; loss of effect and reproductive harm at higher doses; white blood cell and platelet count shifts; genotoxicity concern from anthraquinone content; additive cardiac effect from cardiac glycoside content; reduced platelet aggregation; rebound testosterone drop and androgenic side effects

Monitoring

Marker Target Why
Total testosterone 600–900 ng/dL The endpoint the herb is taken for
Free testosterone 15–25 ng/dL The biologically available fraction
SHBG 20–40 nmol/L Determines how much testosterone is usable
LH 2–6 IU/L Distinguishes a pituitary-driven rise from a testicular one
Estradiol (sensitive assay) 20–30 pg/mL Detects the oestrogen fall seen in rodents
ALT Under 25 U/L Earliest marker of the hepatic signal
AST Under 25 U/L Confirms a hepatic rather than muscle source
ALP and total bilirubin ALP 45–90 U/L; bilirubin 0.3–1.0 mg/dL The pair that moved in the human trial and in rats
eGFR and creatinine eGFR above 90 mL/min/1.73 m² Tracks the renal half of the rodent signal
Lipid panel HDL above 50 mg/dL; triglycerides under 100 mg/dL Tracks the adverse lipid shift seen in rats
CBC with differential Within laboratory reference range Tracks the white cell and platelet movement seen in rats
PSA Under 1.0 ng/mL below age 50 Prostate safety under any androgenic agent

Cadence: Baseline before the first dose, then 4 weeks, then 12 weeks, then every 6 months if use continues. Morning draw between 8 and 10 a.m., fasted.

Qualitative Assessment

  • Morning erection frequency, recorded weekly
  • Libido, rated on a fixed 1–10 scale at the same time each week
  • Training performance: load moved on two fixed compound lifts
  • Energy and motivation through the afternoon
  • Sleep quality and any new palpitations
  • Skin changes, particularly new back or shoulder acne
  • Mood and irritability, ideally noted by someone else as well
Not medical advice. Educational distillation of a single evidence review. Confirm any decision with a qualified clinician, especially in the presence of prescription drugs or chronic conditions.