Last updated: October 2026
Men need 300mg of magnesium a day and women 270mg, according to the NHS, and most people can get it from food. If you take a supplement, the NHS says 400mg or less a day is unlikely to cause harm. For most people, 100 to 300mg of elemental magnesium is plenty to fill a gap.
Below: UK amounts by age, how to read a label (a “500mg magnesium glycinate” capsule is mostly glycine), glycinate and sleep questions, food, safe limits and medicines.
How much magnesium per day, in 30 seconds: 300mg a day (men) or 270mg (women), mostly from food. A supplement of 100 to 300mg of elemental magnesium covers most gaps. Keep supplements to 400mg or less a day, take them with food, and check with your GP or pharmacist first if you have kidney disease or take regular medication.
How much magnesium do you need a day?
UK government figures give a daily amount, the Reference Nutrient Intake (RNI), for every age group. It is enough for nearly everyone in that group, from all sources added together, and it means elemental magnesium, not the weight of a supplement compound.
| Age | Men and boys | Women and girls |
|---|---|---|
| 1 to 3 years | 85mg | 85mg |
| 4 to 6 years | 120mg | 120mg |
| 7 to 10 years | 200mg | 200mg |
| 11 to 14 years | 280mg | 280mg |
| 15 to 18 years | 300mg | 300mg |
| 19 to 64 years | 300mg | 270mg |
| 65 to 74 years | 300mg | 270mg |
| 75 and over | 300mg | 270mg |
There is also a lower figure, the LRNI: 190mg a day for men and 150mg for women. It is enough for only a small minority, so regularly eating less than it means your intake is very likely too low.
Many people in the UK miss the target. In the National Diet and Nutrition Survey (2019 to 2023), women aged 19 to 64 averaged 224mg a day from food, about 83% of the 270mg target, and 15% ate less than the LRNI. Men averaged 273mg, and 20% fell below theirs. Teenage girls fare worst: 48% of girls aged 11 to 18 ate less than the LRNI.
Children: most get enough from food and milk. If you’re thinking about a supplement for a child, read our guide to magnesium for kids and speak to a pharmacist first. Our products are for adults (18+) only.
Pregnancy: if you’re pregnant or breastfeeding, read magnesium in pregnancy and check with your midwife or GP before taking any supplement. We don’t recommend our products during pregnancy or breastfeeding.
The FSA’s 10mg a day figure for CBD is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.
How much magnesium per day for a woman or a man?
Women: 270mg a day from age 19, and the figure doesn’t change at 40, 50, 60 or 70. What changes is how easy it is to reach. In the survey, women aged 65 to 74 averaged 241mg and women 75 and over averaged 231mg, both under target. Our guides to magnesium for women and magnesium for menopause cover each life stage.
Men: 300mg a day from age 19, with no change for men over 50. Regular drinking makes a shortfall more likely (see below). See magnesium for men for the full picture.
Magnesium contributes to a reduction of tiredness and fatigue, normal muscle function and normal psychological function. These are among its authorised health claims in Great Britain.
How much magnesium should you take as a supplement?
A supplement is a top-up for the gap between what you eat and your daily target, so you usually need less than the full 270 or 300mg.
- If you eat wholegrains, nuts, seeds, beans and greens most days, you may not need a supplement at all.
- If your diet is patchy, 100 to 300mg of elemental magnesium a day usually covers the gap.
- Don’t go above 400mg a day from supplements. The NHS says 400mg or less a day is unlikely to cause any harm, and that high doses (more than 400mg) for a short time can cause diarrhoea.
The NHS 400mg and the EFSA 250mg figures
You may also see 250mg quoted as a limit. That comes from the European Food Safety Authority (EFSA), which sets a tolerable upper level of 250mg a day for adults for magnesium from supplements, fortified foods and water. It doesn’t include the magnesium naturally in food and drink. The UK figure most people are given is the NHS one.
In practice, staying around 100 to 250mg from supplements keeps you inside both. Remember to add up every product you take: a multivitamin, a “sleep” blend and a separate magnesium tablet can quietly reach 400mg between them. The magnesium and vitamin D and magnesium and calcium guides explain how to combine them.
Elemental magnesium: how to read a label
Magnesium in supplements is always bound to something else, such as glycine or citric acid. The big number on the front of the pack is often the weight of the whole compound, and only part of it is magnesium. Every daily amount in this guide is elemental magnesium.
On a UK label, look for the line in the nutrition table that says “Magnesium” with a %NRV next to it, often written “magnesium (from magnesium bisglycinate)”. That is the elemental figure. The NRV used on labels is 375mg, so 100mg of magnesium shows as about 27% NRV.
| Form | Roughly how much is magnesium | Magnesium in a 500mg dose of the compound | Compound needed for 100mg magnesium |
|---|---|---|---|
| Glycinate (bisglycinate) | 14% | about 70mg | about 710mg |
| Citrate | 16% | about 80mg | about 620mg |
| Malate | 16% | about 78mg | about 645mg |
| Chloride (hexahydrate) | 12% | about 60mg | about 835mg |
| Taurate | 9% | about 45mg | about 1,120mg |
| L-threonate | 8% | about 41mg | about 1,210mg |
| Oxide | 60% | about 300mg | about 165mg |
We worked these out from each compound’s molecular formula. Real products vary, because some forms are hydrated and some “glycinate” products are buffered with magnesium oxide, so always go by the elemental figure on the label.
A high percentage doesn’t mean better absorption. Oxide packs in the most magnesium per tablet, yet one small study found only about 4% of it was absorbed, compared with much more from chloride, lactate and aspartate. For a side-by-side of every form, see 12 types of magnesium or glycinate vs citrate vs threonate.
How much magnesium glycinate per day?
Go by the elemental magnesium, not the glycinate weight. For most adults that means 100 to 300mg of magnesium a day from glycinate, which is roughly 700 to 2,100mg of magnesium bisglycinate compound.
- “Magnesium glycinate 500mg” per capsule usually means about 70mg of magnesium. Two capsules give about 140mg.
- “Magnesium 100mg (as bisglycinate)” means 100mg of magnesium. That’s the number to count.
- Glycinate and citrate together: add the two elemental figures and keep the total from supplements at 400mg or less.
See our full magnesium glycinate guide for timing and side effects, and how long magnesium takes to work for what to expect over the first few weeks.
Our Magnesium Glycinate Sleep Complex is a berry-flavoured evening drink made with magnesium bisglycinate and magnesium citrate. One 5g serving gives 148mg of elemental magnesium: just over half of a woman’s 270mg and about half of a man’s 300mg, leaving plenty of room for food within the NHS 400mg supplement guide. It also contains glycine, L-theanine, chamomile, passionflower, hops and oat straw, which have no authorised health claims. The product page suggests starting with about a third of a scoop and building up to the full serving.
Magnesium contributes to a reduction of tiredness and fatigue and to normal functioning of the nervous system. The Sleep Complex is for adults (18+) only.
How much magnesium for sleep?
There is no official “sleep dose” of magnesium, and no authorised health claim linking magnesium to sleep. Here’s what the research shows.
- A 2025 trial gave 155 adults who reported poor sleep either 250mg of elemental magnesium a day as bisglycinate or a placebo. After four weeks, insomnia scores improved a little more on magnesium, but the researchers rated the effect as small. People who ate less magnesium to start with seemed to gain most.
- A 2021 review of three small trials in 151 older adults found people fell asleep about 17 minutes sooner on magnesium than on placebo. Total sleep time didn’t change significantly, and the evidence was rated low to very low quality.
The largest recent trial used 250mg of elemental magnesium, inside the NHS supplement guide, not a mega-dose. More is not better, and magnesium isn’t a treatment for insomnia. If poor sleep is affecting your daily life, see your GP.
Magnesium doesn’t knock you out like a sleeping pill; see does magnesium make you sleepy? and the best magnesium for sleep. If restless legs keep you up, read magnesium for restless legs, and for stress and worry, magnesium for anxiety.
Food first: how to reach your daily amount
The NHS says you should be able to get all the magnesium you need from a varied, balanced diet. Figures below are from USDA FoodData Central, for typical UK portions.
| Food and portion | Magnesium |
|---|---|
| Pumpkin seeds, roasted, 30g | 165mg |
| Almonds, roasted, 30g | 84mg |
| Cashews, roasted, 30g | 78mg |
| Spinach, boiled, 90g | 78mg |
| Brown rice, cooked, 180g | 70mg |
| Dark chocolate (70 to 85%), 25g | 57mg |
| Black beans, cooked, 80g | 56mg |
| Porridge oats, 40g dry | 55mg |
| Wholemeal bread, 2 slices (70g) | 53mg |
A sample day: porridge (55mg), two slices of wholemeal toast (53mg), a handful of almonds (84mg), brown rice with beans and spinach at dinner (204mg). That’s nearly 400mg, comfortably past either target, with no supplement. See foods high in magnesium for the full list; many also appear in our high fibre foods guide.
Magnesium from food can’t give you “too much” in the way supplements can: EFSA’s 250mg limit doesn’t apply to magnesium naturally present in food.
Who might be running low?
Mild shortfalls often cause no obvious symptoms. You’re more likely to be low if you:
- eat few wholegrains, nuts, seeds, beans or greens
- drink alcohol regularly. A review found drinking can make the kidneys pass two to three times more magnesium
- take a proton pump inhibitor (such as omeprazole or lansoprazole) long term. The UK medicines regulator says low magnesium has been reported, mostly after a year or more of treatment, and doctors may check your level
- take some diuretics (water tablets), which the same warning flags too
- are a teenage girl or an older adult, the groups whose intakes fall shortest in UK survey data
The regulator lists muscle twitches, tremors, vomiting, tiredness and loss of appetite as symptoms to see a doctor about. Your GP can check your magnesium with a blood test. Read the signs of magnesium deficiency for the full list, and magnesium for energy if tiredness is your main reason for asking.
How much magnesium is too much?
From supplements, more than 400mg a day is where the NHS draws the line, and EFSA’s more cautious limit is 250mg. The first sign of too much is almost always your gut:
- Diarrhoea and loose stools. This is the most common side effect. Citrate and oxide are the forms most likely to do it, which is why they are also used as laxatives (see magnesium for constipation).
- Stomach cramps, wind or bloating, especially on an empty stomach. Our magnesium for bloating guide explains when magnesium can make bloating worse.
Can magnesium glycinate cause diarrhoea? It can, though it is generally reported to be gentler than citrate or oxide. If it happens, cut back, take it with food or split it into two smaller doses.
Much less common is very high blood magnesium (hypermagnesaemia). The BNF lists its signs as nausea, vomiting, flushing, thirst, low blood pressure, drowsiness, confusion, muscle weakness and an irregular heartbeat. Get urgent medical help if you notice these after taking magnesium, especially if you have kidney problems.
Kidney disease: your kidneys clear extra magnesium. The BNF advises caution with magnesium in kidney problems because of the risk of high levels, and to avoid it when kidney function is severely reduced. Don’t take magnesium supplements with kidney disease unless your doctor says so. More in our guides to magnesium side effects and how long magnesium stays in your body.
Medicines to space out from magnesium
Magnesium can stop some medicines being absorbed properly. The BNF gives these timings:
| Medicine | Examples | BNF advice |
|---|---|---|
| Tetracycline antibiotics | Doxycycline, lymecycline, minocycline, oxytetracycline | Separate by at least 2 to 3 hours |
| Alendronic acid (bisphosphonate) | For osteoporosis | Take it at least 30 minutes before magnesium |
| Risedronate (bisphosphonate) | For osteoporosis | Separate by at least 2 hours |
| Ibandronic acid (bisphosphonate) | For osteoporosis | Avoid magnesium for at least 6 hours before and 1 hour after |
If you take any regular medicine, ask your pharmacist to check timings before you start magnesium.
When and how to take magnesium
- Take it with food. It’s kinder to your stomach.
- Split bigger amounts. If you take more than about 200mg, try half in the morning and half in the evening rather than all at once.
- Pick a time you’ll stick to. Being consistent matters more than the clock. Many people take glycinate in the evening as part of a wind-down routine; see the best time to take magnesium.
- Start low and build up over a few days, so you can spot any stomach upset.
- Review after a few weeks. If your diet improves, you may need less.
Choosing between powders, tablets and capsules? Powders make it easy to take a smaller amount; see magnesium powder vs tablets and our best magnesium supplement UK guide.
Sprays and lotions don’t count towards this, as little gets through the skin: see does magnesium spray work?
FAQs
How much magnesium should I take a day?
The NHS says adults need 300mg a day (men) or 270mg (women) in total, mostly from food. If you take a supplement, 100 to 300mg of elemental magnesium usually fills the gap, and 400mg or less a day from supplements is unlikely to cause harm.
How much magnesium glycinate should I take per day?
Count the elemental magnesium, not the glycinate weight. Most adults take 100 to 300mg of magnesium from glycinate, which is roughly 700 to 2,100mg of the compound. A “500mg magnesium glycinate” capsule gives only about 70mg of magnesium.
How much magnesium should I take for sleep?
There is no official sleep dose. A 2025 trial used 250mg of elemental magnesium as bisglycinate and found a small improvement in insomnia scores. Stay at 400mg or less a day from supplements, and see your GP if poor sleep is affecting your daily life.
Is 400mg of magnesium a day too much?
The NHS says 400mg or less a day from supplements is unlikely to cause harm, but more than that can cause diarrhoea. EFSA sets a more cautious 250mg a day limit for supplements. Food magnesium doesn’t count towards either figure.
Can magnesium glycinate cause diarrhoea?
It can, especially at high doses or on an empty stomach, though it is generally reported to be gentler than citrate or oxide. Cut back, take it with food or split the dose into two.
How much magnesium per day for a woman over 50?
The same as younger women: 270mg a day in UK guidance, at 50, 60 and 70 and beyond. Many older women fall short, so food first, then a modest supplement of 100 to 150mg if your diet is light on magnesium.
Can you get too much magnesium from food?
It’s very unlikely. Limits on magnesium apply to supplements, fortified foods and water, not the magnesium naturally in food. Your kidneys clear the extra, which is why people with kidney disease need medical advice before supplementing.
Sources
- NHS. Vitamins and minerals: others (magnesium).
- Public Health England. Government Dietary Recommendations (2016), tables 5 and 6.
- Office for Health Improvement and Disparities. National Diet and Nutrition Survey 2019 to 2023 (chapter 5 tables 5.26 and 5.41).
- EFSA. Summary of Tolerable Upper Intake Levels (magnesium, from SCF 2001).
- Regulation (EU) No 1169/2011 as retained in GB. Annex XIII: nutrient reference values.
- Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register.
- BNF. Magnesium interactions and magnesium glycerophosphate (renal impairment, side effects).
- MHRA. Proton pump inhibitors in long-term use: reports of hypomagnesaemia.
- Schuster J, et al. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nat Sci Sleep, 2025.
- Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults. BMC Complement Med Ther, 2021.
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res, 2001.
- Romani AM. Magnesium homeostasis and alcohol consumption. Magnes Res, 2008.
- PubChem. Magnesium bisglycinate and other compound records (molecular weights used for the elemental magnesium table).
- USDA. FoodData Central (SR Legacy entries 170557, 170158, 170571, 168463, 169704, 170273, 173735, 173904, 172688).
This guide is general information, not medical advice. Evopure makes the Magnesium Glycinate Sleep Complex.
