Last updated: October 2026
Magnesium isn’t a sedative, so it won’t knock you out like a sleeping pill. Some people feel calmer and find it easier to wind down in the evening, especially if their intake is low. Daytime drowsiness from magnesium is uncommon. Citrate and oxide are more likely to send you to the loo than to sleep.
Below: why some people feel sleepy after taking it, which forms are most likely to make a difference, what to do if it makes you tired in the day, how long it takes and the best time to take it.
Why some people feel sleepy after magnesium
Magnesium doesn’t switch your brain off. What researchers have found is that it plays a part in the systems that help you slow down at night:
- GABA and the “alert” receptors. Magnesium acts on GABA, the brain’s main calming messenger, and dampens NMDA receptors, which keep the brain switched on. Researchers think this is one reason it may play a role in sleep.
- Melatonin and cortisol. In a 2012 trial of 46 older adults with insomnia, those taking 500mg of magnesium a day for eight weeks had higher melatonin and lower cortisol in blood tests than those on a placebo.
- Low intake to begin with. The clearest effects show up in people who weren’t getting enough. In a 2025 trial of 155 adults who slept poorly, the biggest gains from magnesium bisglycinate were in people who ate the least magnesium.
Magnesium contributes to the normal functioning of the nervous system and to normal psychological function. That is why many people make it part of an evening wind-down, and why they describe the feeling as “calmer” or “more ready for bed” rather than drowsy.
The evidence for sleep itself is modest. A 2021 review of three trials in 151 older adults with insomnia found people fell asleep about 17 minutes faster on magnesium, but the evidence was rated low to very low quality. In the 2025 trial, insomnia scores improved a little more than on placebo, a small effect. Our full guide to magnesium for sleep goes through every study.
Does the type of magnesium make a difference?
Yes, mostly because of what each form does to your gut. Here is how the common forms compare. There is more on each in our guide to types of magnesium.
| Form | Sleepy? | Gut effect | Best time |
|---|---|---|---|
| Glycinate (bisglycinate) | The form most linked with an evening wind-down, and the one used in the 2025 sleep trial | Very gentle | 30 to 60 minutes before bed |
| Citrate | No more than other forms | Can loosen stools at higher doses | Evening, or earlier in the day if it sends you to the loo |
| Oxide | Very little sleep research; poorly absorbed | Often loosens stools | Not ideal at night |
| L-threonate | Two small trials funded by its makers, with mixed sleep results | Gentle | Morning, or evening if taken for sleep |
| Malate | No; usually taken in the daytime, and not a stimulant either | Gentle | Morning or with lunch |
So if you have asked “does magnesium make you poop or sleep?”, the honest answer is that it depends on the form. Citrate and oxide draw water into the bowel, which is why they are used for constipation and why a big dose at bedtime can wake you up rather than settle you. Glycinate rarely does this.
Can magnesium make you tired during the day?
It isn’t common at usual doses. In the 2025 bisglycinate trial, 93% of people reported no side effects at all, and drowsiness wasn’t among the ones that were reported. If you do feel sluggish, these are the usual reasons:
- Timing. If you take it in the morning and feel slow, switch to the evening. If you take it at night and feel groggy the next morning, take it a little earlier in the evening.
- Dose. Add up the magnesium from every supplement you take, including multivitamins, and lower it if you are near the top of the range.
- Your gut. Loose stools in the night can break up your sleep and leave you tired the next day. A gentler form usually fixes this.
- Something else. Tiredness has many causes, from poor sleep to low iron or an underactive thyroid. See why am I always tired? If you snore loudly and are always sleepy in the day, read about sleep apnoea and see your GP.
It can also work the other way. Feeling tired and weak is one of the early signs of low magnesium, and magnesium contributes to the reduction of tiredness and fatigue. More on that in magnesium for energy.
Can too much magnesium make you drowsy?
Yes, but it is rare. Very high levels of magnesium in the blood (hypermagnesaemia) slow the nervous system down, which can show up as drowsiness and weakness, and in severe cases affects breathing and the heart. A medical review notes that healthy kidneys are very good at clearing extra magnesium, so serious toxicity is exceedingly rare in healthy people. It mostly happens in people with kidney disease or in hospital settings.
If you have kidney disease, speak to your GP before taking any magnesium supplement. If you feel very weak, confused or unwell after taking magnesium, get urgent medical help. Our guide to magnesium side effects covers the rest.
How long does it take for magnesium to make you sleepy?
Some people say they feel calmer on the first evening or two, but magnesium doesn’t work like a pill you take 20 minutes before lights out. In the sleep trials, results were measured after four to eight weeks of daily use. Give it at least two to four weeks of taking it every evening before you judge it. The full timeline by goal is in how long magnesium takes to work.
When to take magnesium, and how much
For sleep, take it 30 to 60 minutes before bed, at the same time each evening, so it becomes a cue that the day is over. For a general top-up, any time you will remember works. There is more detail in the best time to take magnesium, and our 60-minute bedtime routine shows where it fits.
The NHS says adults need 300mg of magnesium a day (men) or 270mg (women), and that 400mg or less a day from supplements is unlikely to cause harm. Higher doses can cause diarrhoea. Check the label for the elemental magnesium figure: 500mg of magnesium glycinate gives roughly 70mg of actual magnesium.
Looking for the best magnesium for sleep in the UK? Start with our quick picks.
An evening magnesium drink
If you would like magnesium as part of your wind-down, our Magnesium Glycinate Sleep Complex is a berry-flavoured drink powder you mix and sip in the evening. Each serving gives 148mg of elemental magnesium from bisglycinate and citrate, well inside the NHS guide, alongside glycine, L-theanine, chamomile, passionflower, hops and oat straw. It’s vegan, made in the UK and third-party lab tested.
Magnesium contributes to the normal functioning of the nervous system and to normal psychological function. It won’t knock you out, and it isn’t meant to: think of it as one calm step in your evening routine.
FAQs
Does magnesium make you sleepy straight away?
Not usually. Magnesium isn’t a sedative. Some people feel calmer on the first evening or two, but in trials, sleep changes were measured after four to eight weeks of daily use.
Does magnesium glycinate make you sleepy or awake?
Neither, really. Glycinate isn’t a stimulant or a sedative. It is the form most people take in the evening because it is gentle on the stomach. If you feel groggy in the morning, take it a little earlier in the evening.
Can magnesium make you tired the next day?
It’s uncommon at usual doses. Try a lower dose or take it earlier in the evening. If you are tired every day, other causes such as poor sleep, low iron or thyroid problems are more likely, so see your GP.
Does magnesium make you poop or sleep?
It depends on the form. Citrate and oxide draw water into the bowel and can loosen stools within hours. Glycinate rarely does, which is why it is the usual evening choice.
Will magnesium make me sleepy if I take it in the morning?
It shouldn’t for most people, because magnesium isn’t a sedative. Malate is often taken in the daytime, and any form works for a general top-up. If a morning dose leaves you sluggish, move it to the evening.
Can too much magnesium make you drowsy?
Very high blood magnesium can cause drowsiness and weakness, but it is very rare in people with healthy kidneys. Keep to 400mg a day or less from supplements, and speak to your GP first if you have kidney disease.
Sources
- NHS. Vitamins and minerals: others (magnesium).
- Mah J, Pitre T (2021). Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies.
- Abbasi B et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences.
- Schuster J et al. (2025). Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nature and Science of Sleep.
- Stewart J, Chen RJ (2026). Magnesium toxicity. StatPearls.
This guide is general information, not medical advice. If you have ongoing sleep problems, speak to your GP. Evopure makes the Magnesium Glycinate Sleep Complex.
