D-aspartic acid is an amino acid sold to prompt the body to make more of its own testosterone. The evidence is thin and conflicting; any benefit is modest, likely brief, and concentrated in men with lower starting testosterone. It is an inexpensive, low-risk experiment far less reliable than sleep, training, and managing body fat. (Full Review)

Protocol

Standard Dose

~2.6–3.0 g/day

D-aspartic acid or sodium D-aspartate; avoid 6 g/day, which may lower testosterone

Best Time of Day

Morning, once daily

Aligns with the natural daily peak of testosterone and luteinizing hormone; no benefit from splitting the dose

Baseline Testing

Test testosterone first

Lower baseline testosterone predicts a greater chance of response, so baseline testing is the most useful pre-protocol step

Time to effect

Testosterone Response

~12 days to a few weeks

The single positive study reported changes within ~12 days; no change on a follow-up test by ~4–6 weeks suggests it is not working

Benefits

Medium: Short-term testosterone increase in untrained or lower-testosterone men

Low: Improved sperm parameters and testosterone in subfertile men

Speculative: Support of LH-driven steroidogenesis as a modulator

Contraindications

Women seeking testosterone effects

Men with hormone-sensitive cancers or conditions (e.g., prostate cancer)

Adolescents

Pregnancy or breastfeeding

Key Interactions

Testosterone replacement therapy or other hormonal agents

Other testosterone or fertility supplements (zinc, magnesium, ubiquinol/CoQ10, Tribulus terrestris, fenugreek, ashwagandha)

Resistance training

Risk & Side Effects

Medium: Testosterone suppression at higher doses

Low: Mild gastrointestinal and general complaints; estradiol shift via aromatase

Speculative: Excitotoxicity concern by analogy to NMDA; long-term safety unknown

Monitoring

Marker	Target	Why
Total testosterone	~500–900 ng/dL (adult men)	Primary outcome; identifies responders and detects suppression
Free testosterone	~15–25 pg/mL (or upper third of lab range)	The bioavailable fraction that drives androgen effects
Luteinizing hormone (LH)	~2–8 mIU/mL	Tests the proposed pituitary mechanism; a rise suggests HPG-axis stimulation
Estradiol (E2)	~10–40 pg/mL (men)	Detects the aromatase-driven shift toward estrogen
SHBG	~20–60 nmol/L	Needed to interpret free testosterone; shifts can mask total-testosterone changes

Cadence: Baseline morning fasting panel before the first dose; repeat at ~4–6 weeks; thereafter every 3–6 months only if continuing use

Qualitative Assessment

Libido and morning erections
Energy and motivation
Mood and sense of well-being
Training drive and recovery

D-Aspartic Acid to Improve Testosterone

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment