L-arginine and ashwagandha: what the evidence says about taking them together

L-arginine and ashwagandha are both sold on a "vitality" or libido-adjacent positioning, but they've never been tested together. L-arginine's clearest evidence in this area is a pooled improvement in erectile function scores; ashwagandha's closest comparison is a small, uncontrolled semen-quality study in men already being evaluated for reduced fertility, at several times a typical capsule dose.

What the evidence doesn't support

It doesn't support a claim that L-arginine and ashwagandha work better together than either alone — that combination has never been tested. It doesn't support carrying either ingredient's trial dose over to a combined product, since neither trial below included the other ingredient. And it doesn't support treating either one as a fertility treatment; concerns about sexual function or fertility are a conversation for a doctor.

What the trials found

A 2024 systematic review and network meta-analysis pooled 15 randomized, placebo-controlled trials in 1,000 men with erectile dysfunction. Compared with placebo, L-arginine on its own was associated with a statistically significant improvement in erectile function scores. The pooled trials were small and varied in dose and duration, and the review's abstract doesn't specify which dose drove the result.

Ashwagandha's nearest comparison trial used a much higher dose in a different, narrower population. Sixty men with reduced sperm counts or motility — heavy smokers, men under psychological stress, or unexplained cases — took 5 grams a day of ashwagandha root powder for three months, with no placebo group, compared against fertile men who received no treatment. Stress markers and several semen-quality measures improved versus baseline. Five grams a day is roughly 3.8 times a typical 1,300 mg/day root-powder capsule dose, and the population — men already being evaluated for reduced fertility — isn't the same as a general population taking a daily supplement.

No study has tested L-arginine and ashwagandha together, at any dose, in any population.

Ingredient	Best evidence	Population	Dose in that trial
L-arginine	Improved erectile function scores vs placebo	1,000 men with erectile dysfunction (15 pooled trials)	Varied; not specified in the pooled abstract
Ashwagandha	Improved semen-quality measures vs baseline, no placebo group	Men with reduced sperm counts/motility (n=60)	5 g/day root powder, 3 months
Both together	No trial exists	—	—

Questions people ask

Can you take L-arginine and ashwagandha together?

There's no trial of the combination, so there's no research describing an added effect. Each ingredient has its own separate safety profile and cautions — ashwagandha in particular carries a caution around thyroid conditions, sedative medication and liver health that L-arginine doesn't — so checking with a doctor before combining them is reasonable, especially around any medication you take.

Is ashwagandha or L-arginine better for libido?

Neither has a trial measuring self-reported libido directly in a general population. L-arginine's best evidence in this area is the erectile-function-score research above; ashwagandha's is the semen-quality study above, in a narrower population. This page doesn't rank the two against each other.

When to talk to a doctor

Concerns about sexual function, semen quality or fertility are worth raising with a doctor for proper evaluation rather than addressing with a supplement pairing first. Neither L-arginine nor ashwagandha is a treatment for a diagnosed reproductive or hormonal condition, and nothing in the evidence above supports using either, alone or combined, as a substitute for medical evaluation.

Related reading: what is L-arginine, does L-arginine raise testosterone, and what is ashwagandha.