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Limited evidencePhysical performance

ZMA

ZMA is zinc, magnesium and B6 in a branded ratio, sold on the promise of higher testosterone and better sleep. Controlled trials in resistance-trained men found no effect on hormones, strength or body composition, and the sleep evidence is weak too; it is only useful if you are actually deficient.

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What the science says

  • Raising testosterone or IGF-1 Limited evidence

    The independent replication attempt is negative: resistance-trained men took ZMA or placebo for 8 weeks alongside training, and there were no differences in total or free testosterone, IGF-1, cortisol, strength, or body composition. The frequently cited positive study in football players was small, manufacturer-affiliated, and has never been reproduced.

  • Improving sleep quality Limited evidence

    A 2024 randomised trial gave zinc magnesium aspartate to men across two consecutive nights of partial sleep deprivation and found no meaningful improvement in sleep quality or in next-day submaximal weightlifting performance. Magnesium alone has better, though still modest, sleep evidence than the ZMA combination.

  • Correcting genuine zinc or magnesium shortfall Moderate evidence

    If you are actually low in zinc or magnesium (plausible in heavy sweaters, restricted-calorie dieters, or vegetarians with high phytate intake), correcting that deficit does restore normal testosterone and neuromuscular function. That is a deficiency correction rather than an ergogenic effect, and it does not require the branded ZMA form.

Dosage & safety

Studied doseThe standard formula is 30 mg zinc (as monomethionine/aspartate), 450 mg magnesium aspartate, and 10.5 mg vitamin B6, taken 30-60 minutes before bed on an empty stomach. Note that 30 mg zinc is already close to the 40 mg/day tolerable upper intake level once dietary zinc is added.
SafetyChronic zinc at 30+ mg/day risks copper deficiency, which can cause anaemia and neurological problems, so do not take indefinitely without accounting for total intake. Zinc on an empty stomach commonly causes nausea. Magnesium aspartate can cause loose stools. Zinc impairs absorption of tetracycline and quinolone antibiotics and of penicillamine; separate doses by 2-4 hours. Not prohibited in sport, though testosterone-marketed products have a poor contamination record generally.

How to take it

Timing30-60 minutes before bed, which is how the formula was designed and studied.
With food?On an empty stomach as the protocol specifies, though this is exactly what causes the nausea — a small snack fixes it at some cost to absorption.
Worth knowing30 mg of zinc plus what you eat sits close to the 40 mg/day upper limit, so treat ZMA as a cycle rather than a permanent fixture.

Interactions

With medications

  • tetracycline and quinolone antibiotics (doxycycline, ciprofloxacin)

    Zinc and magnesium chelate these antibiotics in the gut and substantially reduce how much you absorb. separate by at least 2-4 hours

  • levothyroxine

    Minerals bind levothyroxine and reduce its absorption. separate by at least 4 hours

  • bisphosphonates and penicillamine

    Both are chelated by zinc and magnesium, lowering their effect. separate by at least 2-4 hours

With other supplements

  • copper

    30 mg/day of zinc taken chronically depletes copper, which can cause anaemia and neurological problems. do not run ZMA continuously; if you use it for months, add 1-2 mg copper or take breaks

  • calcium and iron

    These minerals compete with zinc for absorption. take ZMA at bedtime, well away from calcium or iron supplements

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does ZMA increase testosterone?

The evidence is limited and negative: in an 8-week trial in resistance-trained men, ZMA produced no difference from placebo in total or free testosterone, IGF-1, strength or body composition. The positive study often cited was small, manufacturer-affiliated and never reproduced.

Does ZMA help you sleep better?

The sleep evidence for ZMA is limited: a 2024 randomised trial during partial sleep deprivation found no meaningful improvement in sleep quality. Magnesium on its own has better, though still modest, sleep evidence than the ZMA combination.

How do you take ZMA and is it safe to use long-term?

The standard ZMA dose is 30 mg zinc, 450 mg magnesium aspartate and 10.5 mg vitamin B6, taken 30-60 minutes before bed. Because 30 mg of zinc plus dietary zinc sits close to the 40 mg/day upper limit and chronic use risks copper deficiency, treat ZMA as a cycle rather than a permanent supplement.

Does ZMA interact with antibiotics or thyroid medication?

Yes: the zinc and magnesium in ZMA bind tetracycline and quinolone antibiotics, so separate them by at least 2-4 hours, and separate ZMA from levothyroxine by at least 4 hours. Taking ZMA at bedtime also keeps it away from calcium and iron supplements, which compete with zinc.

Scientific references

Where to buy

JYM Supplement Science, ZMA®, Zinc & Magnesium, 90 Vegetarian Capsules

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