Does ZMA work?
Not in the trials so far. Fit men who took it got no extra strength, testosterone or sleep. And a typical ZMA dose is above NHS supplement amounts for all three ingredients.
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Does ZMA work?
ZMA is a mix of zinc, magnesium and vitamin B6. It’s sold to help you sleep, build muscle and raise testosterone.
Five small trials have tested it in active men. None found those gains.
| What was tested | Who took part | What ZMA did |
|---|---|---|
| Strength and muscle | 42 trained men, 8 weeks | No difference in strength, muscle or hormones. The pill also had extra herbs. |
| Testosterone | 14 men who already ate enough zinc | Blood zinc rose. Testosterone didn’t change. |
| Sleep | 19 active men, 2 nights | No effect on sleep. |
| Sleep after 4 or 8 hours in bed | 69 men, 2 nights | About half an hour less sleep, on average. |
| Lifting after short sleep | 16 trained men, 2 nights | No effect on sleep or lifting. |
Sources: Wilborn 2004; Koehler 2009; Edwards 2024; Edwards 2024b; Gallagher 2024
There’s a limit to this. Each trial was small and short. And everyone was a man, and none was chosen for being low in zinc or magnesium.
No trial has tested ZMA in women, or in people who are low. So if you’re buying it for sleep, muscle or testosterone, the trials give you no reason to.
Think you might be low? A zinc blood test or magnesium blood test can check.
Does ZMA help you sleep?
Not in the trials. A team at Liverpool John Moores University tested it three times in 2024.
Men took 30mg zinc, 450mg magnesium and 10.5mg B6 before bed for two nights. A movement tracker measured their sleep.
In normal sleepers, ZMA had no effect on sleep. After nights of only 4 hours, it still didn’t help. One trial found men slept about half an hour less on ZMA.
One study did find better sleep, in care home residents aged about 78 with insomnia (long-term trouble sleeping). But that pill also had 5mg of melatonin, a sleep hormone. So it tells you little about ZMA.
Want to try magnesium on its own? See magnesium for sleep. And start with the free fixes in sleep hygiene.
Does ZMA boost testosterone or muscle?
Not in men who already eat enough zinc. In 14 men who exercised often, ZMA raised blood zinc. Their testosterone (total and the free, active part) didn’t change.
An 8-week trial in 42 men who lift weights found no extra strength on the bench or leg press. Muscle and hormones didn’t change either. A supplement company paid for that trial.
People who are low in zinc are a different case, and no ZMA trial has tested them. For what the single minerals do, see zinc and testosterone and magnesium and testosterone.
Your next step for muscle: put the money into food and training. See supplements for muscle building for what has better evidence.
How much zinc and magnesium is safe?
| Ingredient | ZMA dose in trials | NHS supplement limit |
|---|---|---|
| Zinc | 30mg | No more than 25mg a day, unless a doctor advises it. |
| Magnesium | 450mg | 400mg or less a day is unlikely to cause harm. |
| Vitamin B6 | 10.5mg | No more than 10mg a day, unless a doctor advises it. |
Sources: NHS: zinc and magnesium; NHS: vitamin B6; Edwards 2024
That’s the catch from the top of this page. Three capsules of a UK ZMA product, the dose the trials used, go just above each NHS amount.
Too much zinc cuts how much copper you absorb. That can lead to anaemia (too few healthy red blood cells) and weaker bones. More than 400mg of magnesium for a short time can cause diarrhoea.
Taking 200mg or more of B6 a day can cause a loss of feeling in the arms and legs. The effect of 10mg to 200mg is unclear.
- 25 mg a day or belowWithin the NHS limit.
- Above 25 to just under 50 mg a dayOver the limit. Only if a doctor advises it.
- 50 mg a day or aboveStomach upset reported from 50mg a day.
Sources: NHS; Devarshi 2024
Your next step: add up the zinc, magnesium and B6 in everything you take, including a multivitamin.
Should you take zinc and magnesium tablets?
Most people don’t need to. The NHS says you should be able to get all the zinc and magnesium you need from a varied, balanced diet.
Adult men need about 9.5mg of zinc a day and women about 7mg. For magnesium, it’s 300mg for men and 270mg for women aged 19 to 64.
Zinc comes from meat, shellfish, cheese, bread and wheatgerm, and magnesium from spinach, nuts and wholemeal bread.
Some people are more likely to run low on zinc, says a review by a supplement maker. That includes people who eat mainly plants, are pregnant or breastfeeding, are older, or have a bowel condition. It also includes people who’ve had weight-loss surgery or are dependent on alcohol.
Before you buy zinc and magnesium tablets
- Check the label for how many mg of each mineral you get, not just the name.
- Take no more than 25mg of zinc a day from supplements, unless a doctor advises it.
- Keep magnesium from supplements to 400mg a day or less.
- Take no more than 10mg of vitamin B6 a day from supplements, unless a doctor advises it.
- Add up every supplement you take, including a multivitamin.
- On doxycycline (an antibiotic)? Tell your doctor first, as zinc may not mix well with it.
Sources: NHS: zinc and magnesium; NHS: vitamin B6; NHS: doxycycline
Choosing a type? See which magnesium to take and how much zinc to take.
When to speak to a GP
Speak to a GP or pharmacist if:
- You take the antibiotic doxycycline. Supplements with zinc may not mix well with it.
- You’ve taken more than 25mg of zinc a day from supplements without a doctor’s advice. High doses can lead to anaemia.
- You lose feeling in your arms or legs while taking vitamin B6. This usually improves once you stop.
- You eat mainly plants, have a bowel condition or had weight-loss surgery, and want your zinc checked.
Never stop or change a prescribed medicine without your prescriber.