D-Aspartic Acid
Summary
D-aspartic acid is an amino acid found in the pituitary gland and testes. One uncontrolled-allocation 2009 study reported higher testosterone after 12 days in untrained men. Four later randomized trials in trained men found no testosterone rise at 3–6 g/day or strength benefit, and a fifth found that 6 g/day lowered testosterone.
Key facts
- The D-form of aspartic acid, occurring mainly in the pituitary and testes; in rats it is made there from L-aspartate by a racemase[1]
- 6 g/day for 14 days lowered total and free testosterone in one trial of 24 men[3]
- 3.12 g/day for 12 days raised testosterone 42% in 23 untrained men; randomization was not described[1]
- Human results are inconsistent and based on few, small studies; a 2024 review found most testosterone boosters fail to raise total testosterone[7][8]
- 7 graded human outcomes on this page
- October 13, 2026
How it works
ProposedIn rats and isolated rat tissue, D-aspartate raised LH release from the pituitary (via cGMP) and testosterone synthesis in Leydig cells (via cAMP). Whether oral doses do this in men is unsettled: most trials in trained men saw no hormone change.[1][7]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Fertility | Grade D | Improved | RCT · n = 48 · 2025 | 1 row |
| Testosterone | Grade D | Improved | Open-label · n = 43 · 2009 | 6 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Sperm motility and testosterone in idiopathic male infertility (combination) | Improved | Grade D | RCT · n = 48 · 2025 Men with idiopathic infertility (Egypt) Form: Combination: D-aspartic acid, ubiquinol and zinc · Dose: 2,660 mg D-aspartic acid + 200 mg ubiquinol + 10 mg zinc daily · Duration: 3 months Progressive sperm motility improved (10.6% to 15.2%, P=0.047) and total testosterone rose (5.06 to 5.89, P=0.009) in the combination group. | 40248985 (opens PubMed)Source [9] |
| Serum testosterone and LH in healthy untrained men | Improved | Grade D | Open-label trial · n = 43 · 2009 Healthy men aged 27–37 at an IVF unit (Italy) Form: Sodium D-aspartate solution with vitamins B6, B12 and folic acid · Dose: 3.12 g/day sodium D-aspartate · Duration: 12 days Testosterone rose from 4.5 to 6.4 ng/mL (about 42%) and LH by about 33% in the D-aspartate group; the placebo group did not change. | 19860889 (opens PubMed)Source [1] |
| Total and free testosterone in resistance-trained men (3 g vs 6 g) | Worsened | Grade D | RCT · n = 24 · 2015 Men with at least two years of resistance training (Australia) Form: D-aspartic acid · Dose: 3 g/day or 6 g/day vs 6 g/day flour placebo · Duration: 14 days 3 g/day had no effect on testosterone. 6 g/day lowered total testosterone and lowered free testosterone compared with placebo (P=0.005). | 25844073 (opens PubMed)Source [3] |
| Testosterone, LH and strength in resistance-trained men | No effect | Grade D | RCT · n = 20 · 2013 Resistance-trained men during 28 days of heavy training (USA) Form: D-aspartic acid · Dose: 3 g/day · Duration: 28 days Total and free testosterone, LH, GnRH and estradiol did not change; strength and body composition improved equally with placebo. | 24074738 (opens PubMed)Source [2] |
| Testosterone, strength and muscle size over 12 weeks of training | No effect | Grade D | RCT · n = 19 · 2017 Resistance-trained men aged 18–36 (Australia) Form: D-aspartic acid · Dose: 6 g/day · Duration: 12 weeks No change in total or free testosterone. Estradiol fell 16% with D-aspartic acid. Strength and muscle growth increased similarly in both groups. | 28841667 (opens PubMed)Source [4] |
| Testosterone, LH and physical function in male climbers | No effect | Grade D | Crossover RCT · n = 16 · 2019 Male climbers continuing normal training (Poland) Form: D-aspartic acid · Dose: 3 g/day · Duration: 2 weeks per arm Serum testosterone, calculated free testosterone and LH did not change versus placebo; physical function and hematology also did not respond. | 29893592 (opens PubMed)Source [5] |
| Testosterone, cortisol and blood counts in boxers at simulated altitude | No effect | Grade D | RCT · n = 16 · 2023 Male boxers sleeping in normobaric hypoxia (Poland) Form: D-aspartic acid · Dose: 6 g/day · Duration: 14 days No significant effect on resting testosterone, LH or the testosterone/cortisol ratio, and no added effect on red blood cell changes. | 38201906 (opens PubMed)Source [6] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| D-aspartic acid (free acid) powder or capsules | Varies[2][3][4][5] | No human pharmacokinetic study was found; one trial measured only a slight, non-significant rise in serum D-aspartate after 28 days.[2] | No adverse events attributed to D-aspartic acid were reported in the trial abstracts; physical function and blood counts did not change in one 2-week crossover.[4][5] | Testosterone and training trials at 3–6 g/day |
| Sodium D-aspartate | Varies[1] | Studied as a 2 M oral solution (3.12 g per 10 mL) with B vitamins; no head-to-head human absorption data against the free acid.[1] | No adverse effects are reported in the 2009 study.[1] | One 12-day testosterone study in untrained men |
Studied doses
Doses studied in human trials ranged from 2,660 mg/day (inside a zinc and ubiquinol combination) and 3 g/day up to 6 g/day, for 12 days to 3 months. The only clearly positive testosterone result used 3.12 g/day of sodium D-aspartate for 12 days.[1][2][3][4][5][6][9]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Expecting higher testosterone
- Randomized trials in resistance-trained men found no testosterone rise, and 6 g/day lowered testosterone in one 2-week trial.[2][3][4]
- Hormone therapy or hormone-sensitive conditions
- D-aspartic acid shifted reproductive hormones in trials: LH and testosterone rose in a 2009 study, 6 g/day lowered testosterone over 2 weeks, and estradiol fell 16% over 12 weeks. No trial enrolled people on testosterone or other hormone therapy, or with hormone-sensitive conditions.[1][3][4]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- Label dose vs studied dose3 g/day, the most-studied amount, showed no testosterone effect in three trials of trained men; the 2009 positive study used 3.12 g of sodium D-aspartate.[1][2][3][5]
- More is not betterDoubling to 6 g/day did not help in two trials and lowered testosterone in one.[3][4][6]
- BlendsThe fertility result came from a blend with ubiquinol and zinc, so it says little about D-aspartic acid alone.[9]
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Cost per studied dose
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Frequently asked questions
Does D-aspartic acid raise testosterone?
Not in trained men. Four randomized trials at 3–6 g/day found no rise. A 2009 study in untrained men reported a 42% increase after 12 days, but it did not describe randomization.[1][2][4][5][6]
Can D-aspartic acid lower testosterone?
In one trial, 6 g/day for 14 days lowered total and free testosterone in resistance-trained men; 3 g/day had no effect.[3]
Does D-aspartic acid build muscle or strength?
No. In 28-day and 12-week training trials, strength and muscle size rose equally with placebo.[2][4]
Does D-aspartic acid help male fertility?
One 2025 trial in infertile men found better sperm motility with a blend of 2,660 mg D-aspartic acid, ubiquinol and zinc, so its own effect is unknown.[9]
How much D-aspartic acid was studied?
Trials used 3 g/day or 6 g/day for 12 days to 3 months; neither dose raised testosterone in trained men.[2][3][4][5][6]
Is D-aspartic acid the same as L-aspartic acid?
No. They are mirror-image forms. In rats, a racemase in the pituitary and testes converts L-aspartate into D-aspartate.[1]
Sources
- [1]The role and molecular mechanism of D-aspartic acid in the release and synthesis of LH and testosterone in humans and rats.. Reprod Biol Endocrinol, 2009. open-label
- [2]D-aspartic acid supplementation combined with 28 days of heavy resistance training has no effect on body composition, muscle strength, and serum hormones associated with the hypothalamo-pituitary-gonadal axis in resistance-trained men.. Nutr Res, 2013. RCT
- [3]Three and six grams supplementation of d-aspartic acid in resistance trained men.. J Int Soc Sports Nutr, 2015. RCT
- [4]The effects of d-aspartic acid supplementation in resistance-trained men over a three month training period: A randomised controlled trial.. PLoS One, 2017. RCT
- [5]Short-Term d-Aspartic Acid Supplementation Does Not Affect Serum Biomarkers Associated With the Hypothalamic-Pituitary-Gonadal Axis in Male Climbers.. Int J Sport Nutr Exerc Metab, 2019. crossover-RCT
- [6]The Effects of Six-Gram D-Aspartic Acid Supplementation on the Testosterone, Cortisol, and Hematological Responses of Male Boxers Subjected to 11 Days of Nocturnal Exposure to Normobaric Hypoxia.. Nutrients, 2023. RCT
- [7]The putative effects of D-Aspartic acid on blood testosterone levels: A systematic review.. Int J Reprod Biomed, 2017. systematic-review
- [8]Do "testosterone boosters" really increase serum total testosterone? A systematic review.. Int J Impot Res, 2024. systematic-review
- [9]Evaluation of in vivo supplementation of 2660 mg D-aspartic acid and 200 mg ubiquinol and 10 mg zinc on different semen parameters in idiopathic male infertility: a randomized double blind placebo controlled study.. Arch Ital Urol Androl, 2025. RCT
What changed
- Independent review: added a hormone-therapy / hormone-sensitive caution from the hormone shifts in the cited trials; corrected the baseline-testosterone insight (4.5 ng/mL is not the low end of normal; Melville 2015 found no baseline-response correlation, r=0.10); scoped the "failed to repeat" insight to trials of D-aspartic acid alone. All PMIDs re-checked.
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows. Abstracts read for all 9 PMIDs; Topo 2009 dose (3.12 g sodium D-aspartate), percentages and lack of described randomization checked in the full text (PMC2774316); Willoughby 2013 sample size taken from the 2017 systematic review. Page set indexable.