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ZMA Supplements: What the Trials Show for Sleep, Testosterone and Strength

ZMA, a zinc, magnesium and vitamin B6 blend, has not held up in later trials. In 42 trained men, a ZMA product with added herbs did not raise testosterone, strength or muscle more than a placebo (grade C), and three small two-night trials in healthy young men found no better sleep (grade C). The one positive trial was never repeated. Its usual 450 mg of magnesium is above the adult upper limit of 350 mg from supplements.

Published How we grade evidenceEditorial policy

ZMA is a zinc, magnesium and vitamin B6 blend sold as ZMA, usually as capsules taken before bed. In the trials, a day's dose gave 30 mg of zinc, 450 mg of magnesium and 10.5 to 11 mg of vitamin B6 (Wilborn 2004; Gallagher 2024).

The short version

  • Testosterone: no rise in 42 trained men over 8 weeks against a placebo, or in 14 exercising men who already ate enough zinc. Grade C for no effect (Wilborn 2004; Koehler 2009).
  • Strength and muscle: no difference from placebo in bench press, leg press, sprint power or lean mass in the same 42 trained men. Grade C for no effect (Wilborn 2004).
  • Sleep: three small two-night trials in healthy young men, with and without short sleep, found no better sleep than a placebo; one found shorter sleep. Grade C for no benefit (Gallagher 2024; Edwards 2024a; Edwards 2024b).
  • The ingredients alone: zinc raised testosterone only in a tiny study of older men short of zinc (grade D, Prasad 1996); magnesium may help older adults fall asleep a little sooner, in weak trials (grade C, Mah 2021).
  • Safety: the usual 450 mg of magnesium is above the 350 mg adult upper limit for supplements, and both minerals cut the uptake of some antibiotics, magnesium also of osteoporosis pills (Costello 2023; NIH ODS).
Question (who, compared with what)What trials foundSize of effectGrade
Testosterone (healthy trained or exercising men; vs placebo in one trial)No changeNone foundC
Strength, power, body composition (42 trained men, vs placebo, 8 weeks)No differenceNone foundC
Sleep (healthy young men, two nights; vs placebo and no pill)No benefit; one trial shorter sleepAbout half an hour less in one trialC
Zinc alone for testosterone (9 older men low in zinc, no placebo)RoseOne small studyD
Magnesium alone for falling asleep (2 trials, 55 older adults, vs placebo)A little soonerAbout 17 minutes, low qualityC

Does ZMA work?

Not in any trial since the first. The idea came from one 2000 study in football players, published by Brilla and Conte in an online exercise journal that PubMed does not index. It reported larger gains in testosterone, a growth hormone marker called IGF-1, and leg strength on ZMA than on a placebo, as later trials describe it (Wilborn 2004; Gallagher 2024). It has not been repeated: later trials by other groups found no benefit. All enrolled men; none of these trials included women.

Does ZMA raise testosterone?

Grade C for no rise. In a double-blind trial, 42 men who already lifted weights took either ZMA capsules or a sugar placebo before bed for 8 weeks of set training. Blood zinc went up 11 to 17%, a change too small to rule out chance, and testosterone and other muscle-building and muscle-breakdown hormones did not differ between the groups (Wilborn 2004). That product also held a seed extract with 50 mg of L-dopa and a plant steroid extract; its seller funded the study, which the lab says it ran independently.

A German study gave ZMA to 14 healthy men aged 22 to 33 who exercised and ate enough zinc. Blood zinc rose, but total and free testosterone did not change, and neither did the pattern of testosterone breakdown products in urine (Koehler 2009). The ZMA page shows D for this outcome; a placebo-controlled trial plus a second study pointing the same way meet the site's C, and that matches how our low testosterone guide rates the Koehler study.

Does ZMA help you build muscle or get stronger?

Grade C for no effect. In the same 8-week trial of 42 trained men, the herb-added ZMA product made no difference to one-rep maximum bench press or leg press, muscle endurance, or cycling sprint power, compared with the placebo. Body fat and lean mass, measured by a DEXA body scan, did not differ either (Wilborn 2004). The ZMA page shows D for strength and body composition; a 42-person placebo-controlled trial meets the site's C rather than D, though it is still only one trial.

A 2024 crossover study, in which each man took ZMA, a placebo and no pill on separate occasions, found higher jumps after two nights of ZMA than after the placebo, but not compared with taking nothing; sprints did not change (Edwards 2024b). For training aids with better evidence, see our sports performance guide.

Does ZMA help you sleep?

Grade C for no benefit. Three small 2024 studies from one university lab in England tested the blend over two nights in healthy, well-fed young men, using a placebo and a no-pill condition for comparison. The authors reported no conflicts of interest, and one of the papers says the lab bought the ZMA itself.

  • Short sleep: in 16 trained men allowed only 4 hours of sleep for two nights, ZMA did not improve sleep, morning weightlifting or tiredness ratings (Gallagher 2024).
  • Short or normal sleep: in two groups of men, 33 allowed 4 hours of sleep and 36 allowed 8 hours, ZMA did not help a morning attention test, and total sleep was about half an hour shorter on ZMA than on the other two conditions, nearly an hour shorter in the 8-hour group (Edwards 2024a).
  • Normal sleep: in 19 active men who slept normally, two nights of ZMA had no effect on sleep, sprints or the attention test (Edwards 2024b).

These short trials in men without sleep problems can't say what weeks of ZMA would do in insomnia. The ZMA page also shows C, no effect, for sleep.

Does the magnesium or zinc in ZMA help on its own?

Each mineral alone has thin evidence, mostly in older people or those short of it.

  • Magnesium and sleep, grade C. In a review of 3 small placebo-controlled trials (151 older adults), the two that measured it (55 people) found oral magnesium cut the time to fall asleep by 17.36 minutes, though all three trials were at moderate to high risk of bias (Mah 2021). Looking at 12 trials of magnesium alone, a 2026 review judged the results inconsistent and the certainty low to very low, and found the evidence did not support routine use for insomnia (Lopresti 2026). Our sleep supplements compared guide gives the same grade.
  • Zinc and testosterone, grade D. In 9 older men who were mildly short of zinc, testosterone rose from 8.3 to 16.0 nmol/L after zinc for up to 6 months, in a study without any placebo (Prasad 1996). If your zinc intake is already adequate, the ZMA studies above suggest extra zinc won't change it. Our zinc guide covers who runs low.
  • Magnesium and testosterone, grade D. Testosterone rose over 4 weeks in tae kwon do athletes and sedentary men given magnesium, in a study with no placebo (Cinar 2011).
  • A melatonin, magnesium and zinc mix, in older people with insomnia. In 43 care-home residents averaging 78 years, a nightly mix of 5 mg melatonin, 225 mg magnesium and 11.25 mg zinc in pear pulp for 8 weeks improved sleep quality scores and total sleep time more than pear pulp alone (Rondanelli 2011). Melatonin was part of it, so the minerals can't take the credit; those mineral amounts sit below their adult upper limits.

When should you take ZMA, and how much is in it?

The trials that report timing gave the capsules 30 to 60 minutes before bed (Wilborn 2004; Edwards 2024b), but with no benefit found, timing matters less than the amounts:

  • Magnesium, 450 mg a day: above the limit. Upper limit for adults: magnesium from supplements, 350 mg daily, set to avoid diarrhoea (sometimes with nausea and cramps); take more only with blood tests or your clinician's advice (NIH ODS; Costello 2023; check your stack).
  • Zinc, 30 mg a day: below the limit on its own, but stacks add up. Upper limit for adults: 40 mg of zinc a day, since more can cause copper deficiency, which mainly damages blood and nerves; one case report describes severe anaemia from zinc pills draining copper (NIH ODS; Magham 2023).
  • Vitamin B6, 10.5 to 11 mg a day: below the US limit of 100 mg a day and just under the 12 mg a day that the European Food Safety Authority set for adults in 2023; both limits guard against nerve damage, the numbness and unsteadiness that high B6 can cause (NIH ODS; EFSA 2023).

What we'd skip

  • ZMA to raise testosterone, strength or muscle in men who eat a normal diet. The placebo-controlled trial and the hormone study found no effect (Wilborn 2004; Koehler 2009).
  • ZMA as a sleep aid for healthy adults. Three small trials found no benefit, and one found shorter sleep (Edwards 2024a). For low testosterone itself, see the low testosterone page.
  • "Testosterone booster" stacks built on ZMA. Muscle-building products are among those most often found to contain hidden drugs (below).

Safety and interactions

  • Diarrhoea: the magnesium is the usual cause (see the amounts above); the 2004 trial reported no clinical side effects over 8 weeks (Wilborn 2004).
  • Kidney disease: with weak kidneys, magnesium can build up in the blood. In a case series of 4 people over 65 with kidney problems who took magnesium oxide as a laxative, magnesium rose high enough to cause symptoms, and one of them died (Yamaguchi 2019). If you have kidney disease, ask your kidney team before taking ZMA or any magnesium product.
  • Antibiotics: zinc and magnesium bind tetracycline antibiotics (such as doxycycline) and quinolone antibiotics (such as ciprofloxacin) and cut how much you absorb. Swallow the antibiotic 2 or more hours before ZMA, or 4 to 6 hours after it (NIH ODS zinc; NIH ODS magnesium).
  • Osteoporosis pills (bisphosphonates such as alendronate): keep magnesium at least 2 hours away from them (NIH ODS).
  • Penicillamine (for Wilson disease or rheumatoid arthritis): zinc lowers its absorption; take them at least 1 hour apart (NIH ODS).
  • Levothyroxine: minerals such as magnesium can lower how much thyroid medicine you absorb; see can I take iron, calcium or magnesium with levothyroxine? and ask your prescriber or pharmacist about spacing.
  • Water pills and blood pressure medicines: thiazide water pills increase zinc loss in urine, and some water pills change magnesium levels (NIH ODS zinc; NIH ODS magnesium); see can I take magnesium with blood pressure medicine?.
  • Calcium and iron pills: ask your pharmacist how to space them from ZMA.
  • Vitamin B6 and lung cancer, observational: in a US study of 77,118 people aged 50 to 76, men who took B6 on its own at more than 20 mg a day over 10 years had a higher lung cancer risk (hazard ratio 1.82), more so in smokers, while women showed no link. This kind of study can't prove cause; ZMA alone stays under 20 mg, but an extra B6 pill would pass it (Brasky 2017).
  • Hidden drugs in sports supplements: a 2026 review of 44 studies found about 9 to 15% of tested sports supplements held banned substances or unlisted drugs, mostly stimulants and steroid-like agents, most often in products sold for workouts, weight loss or muscle (Al-Saad 2026). If you are drug-tested, use a product tested batch by batch by an independent lab.
  • Pregnancy: ask your midwife or obstetric team before taking ZMA or any zinc or magnesium product, and take only what they advise.
  • Breastfeeding? Zinc is a normal part of breast milk (LactMed: Zinc), but ask your midwife, doctor or a lactation specialist, who can check what passes into breast milk, before using a blend.
  • Children and teens: untested; ask your child's doctor.

When to see a doctor

  • Emergency (911) for very weak muscles, trouble breathing, an irregular heartbeat, fainting or extreme drowsiness after taking magnesium products, especially with kidney disease; these can be signs of dangerously high blood magnesium (NIH ODS).
  • Soon for numbness, tingling or unsteadiness in your hands or feet (possible nerve damage from B6 or from low copper after long zinc use), unusual tiredness or paleness that could mean anaemia, or diarrhoea that won't settle within a few days.
  • Book a check if you took ZMA for low energy, low sex drive or poor sleep: low testosterone, sleep apnoea, depression and thyroid problems need testing, and a blood test can show low zinc or magnesium (insomnia; low testosterone).

Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. Pregnant or breastfeeding? Ask your midwife or obstetric team first. Under 18? Ask a clinician.

FAQ

Does ZMA really work? Not in later trials. In 42 trained men, a ZMA product with added herbs did not raise testosterone, strength or muscle more than a placebo (grade C), and three two-night trials in healthy young men found no sleep benefit (grade C). The positive 2000 football study has never been repeated, and PubMed does not index the journal it appeared in.

Does ZMA increase testosterone? No rise was seen in 42 trained men on ZMA against a placebo, or in 14 exercising men who already ate enough zinc (grade C). In a tiny study, zinc raised testosterone only in older men with marginal zinc deficiency (grade D).

Is ZMA good for sleep? Three small trials in healthy young men, over two nights each, found no better sleep than a placebo, and one found about half an hour less sleep (grade C). Magnesium alone may help older adults fall asleep a little sooner (grade C).

What are the side effects of ZMA? Its usual 450 mg of magnesium is above the 350 mg adult limit for supplements and can cause diarrhoea. Zinc above 40 mg a day can cause copper deficiency. Both minerals reduce the absorption of some antibiotics, and magnesium can also lower the uptake of osteoporosis pills and thyroid medicine.

When should I take ZMA? The trials that report timing gave it 30 to 60 minutes before bed. Since none found a benefit, spacing matters more: take tetracycline or quinolone antibiotics 2 or more hours before it or 4 to 6 hours after, and keep it at least 2 hours from osteoporosis pills.

Sources

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  2. Koehler K, et al. Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. Eur J Clin Nutr. 2009. PubMed 17882141 · doi:10.1038/sj.ejcn.1602899
  3. Gallagher C, et al. Effects of Supplementing Zinc Magnesium Aspartate on Sleep Quality and Submaximal Weightlifting Performance, following Two Consecutive Nights of Partial Sleep Deprivation. Nutrients. 2024. PubMed 38257144 · doi:10.3390/nu16020251
  4. Edwards BJ, et al. In Males with Adequate Dietary Needs Who Present No Sleep Disturbances, Is an Acute Intake of Zinc Magnesium Aspartate, Following Either Two Consecutive Nights of 8 or 4 h of Sleep Deprivation, Beneficial for Sleep and Morning Stroop Interference Performance? Behav Sci (Basel). 2024. PubMed 39062445 · doi:10.3390/bs14070622
  5. Edwards BJ, et al. Effects of an Acute Dose of Zinc Monomethionine Asparate and Magnesium Asparate (ZMA) on Subsequent Sleep and Next-Day Morning Performance (Countermovement Jumps, Repeated Sprints and Stroop Test). Nutrients. 2024. PubMed 39125347 · doi:10.3390/nu16152466
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  8. Costello R, et al. Perspective: Call for Re-evaluation of the Tolerable Upper Intake Level for Magnesium Supplementation in Adults. Adv Nutr. 2023. PubMed 37487817 · doi:10.1016/j.advnut.2023.06.008
  9. Lopresti AL, et al. Magnesium Supplementation for Sleep in Adults: A Systematic Review of Randomized Controlled Trials. J Diet Suppl. 2026. PubMed 42661485 · doi:10.1080/19390211.2026.2719670
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  11. Rondanelli M, et al. The effect of melatonin, magnesium, and zinc on primary insomnia in long-term care facility residents in Italy: a double-blind, placebo-controlled clinical trial. J Am Geriatr Soc. 2011. PubMed 21226679 · doi:10.1111/j.1532-5415.2010.03232.x
  12. Magham K, et al. Severe copper deficiency anemia caused by zinc supplement use. Am J Emerg Med. 2023. PubMed 37640593 · doi:10.1016/j.ajem.2023.08.033
  13. Yamaguchi H, et al. Severe hypermagnesemia induced by magnesium oxide ingestion: a case series. CEN Case Rep. 2019. PubMed 30136128 · doi:10.1007/s13730-018-0359-5
  14. Brasky TM, et al. Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort. J Clin Oncol. 2017. PubMed 28829668 · doi:10.1200/JCO.2017.72.7735
  15. Al-Saad N, et al. Systematic review of undeclared prohibited substances and pharmacological adulterants in dietary supplements: prevalence, detection, and risks in sport. Front Sports Act Living. 2026. PubMed 41908212 · doi:10.3389/fspor.2026.1740663
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