Last updated: October 2026
Magnesium citrate is magnesium bound to citric acid. It is one of the better-absorbed forms, contains roughly 11 to 16% magnesium by weight, and draws water into the bowel, so higher amounts loosen stools. The NHS says 400mg or less a day of magnesium from supplements is unlikely to cause harm. Take it with food, morning or night.
Below: what magnesium citrate is used for, how much real magnesium you get, the laxative effect, side effects, who should check first, and how it compares with glycinate and oxide.
In short: magnesium citrate is a good everyday form if you want well-absorbed magnesium and don’t mind, or would welcome, a mild loosening effect on the bowel. If you have a sensitive stomach, glycinate is usually gentler. Always check the label for the elemental magnesium figure, not the weight of the compound.
What is magnesium citrate?
Every magnesium supplement is magnesium joined to a partner molecule. In magnesium citrate, that partner is citric acid, the same acid found in lemons. The partner matters because it changes three things: how much magnesium you get per gram, how well it dissolves and is absorbed, and how it feels on your stomach.
Citrate is an “organic” salt, meaning the magnesium is bound to an organic acid rather than to oxygen (oxide) or carbonate. Organic forms such as citrate and glycinate tend to dissolve well, which is one reason citrate is among the most popular forms sold in the UK. For the full line-up, see our guide to types of magnesium.
| Magnesium citrate at a glance | |
|---|---|
| Bound to | Citric acid |
| Magnesium content | Roughly 11 to 16% by weight, depending on the form used |
| Absorption | Good: better than oxide in head-to-head studies |
| Effect on the bowel | Mild at everyday amounts; loosens stools at higher amounts |
| Forms sold | Capsules, tablets, powders and drinks; also in some bowel preparations |
| UK supplement guide | 400mg or less a day of magnesium from supplements (NHS) |
What is magnesium citrate used for?
People choose magnesium citrate for two broad reasons: to top up their magnesium intake with a well-absorbed form, and, at higher amounts, for its effect on the bowel. Here is what it can and can’t do for the most searched uses.
- Everyday magnesium top-up. Magnesium contributes to the reduction of tiredness and fatigue, to normal muscle function and to the maintenance of normal bones. If your diet is low in green vegetables, nuts, seeds and wholegrains, a supplement is one way to fill the gap. See signs of magnesium deficiency.
- Sleep. No form of magnesium has an authorised sleep claim. Magnesium contributes to normal functioning of the nervous system, which is why many people include it in an evening routine. The research on magnesium and sleep is mixed; we cover it honestly in magnesium for sleep. Citrate’s bowel effect makes glycinate the more common bedtime choice.
- Stress and anxiety. Magnesium contributes to normal psychological function. It isn’t a treatment for anxiety. See magnesium for anxiety.
- Cramps. Magnesium contributes to normal muscle function, but a Cochrane review of trials in mostly older adults with night-time leg cramps found magnesium made little or no difference to how often cramps happened. More in magnesium for cramps.
- Bloating and water retention. Magnesium contributes to electrolyte balance. If bloating comes from constipation, citrate’s loosening effect may be relevant; if you are prone to loose stools, it can make bloating worse. See magnesium for bloating and magnesium for water retention.
- Constipation. Covered in the next section.
Magnesium citrate for constipation: how the laxative effect works
Magnesium citrate works as an osmotic laxative. Any magnesium that isn’t absorbed stays in the bowel and pulls water in from the body. That extra water softens stools and makes them easier to pass. The NHS describes osmotic laxatives in the same way and says they usually take 2 to 3 days to work, and that you should drink plenty of fluids while taking them to avoid dehydration.
The effect depends on the dose. At everyday supplement amounts most of the magnesium is absorbed and many people notice little change, or just slightly softer stools. At larger amounts, more is left in the gut and the effect gets stronger. This is the same reason the NHS warns that high doses of magnesium, over 400mg for a short time, can cause diarrhoea.
Some things to know before using it this way:
- Try the basics first. The NHS advice for constipation starts with more fibre, more fluids and more activity.
- Short-term only. For laxatives bought without a prescription, the NHS says to stop when your constipation improves and not to use them for longer than 7 days.
- Ask a pharmacist which laxative suits you. Licensed laxatives have clear dosing; supplements are not designed or tested as laxatives.
- See a GP if constipation keeps coming back, you need laxatives regularly, or you notice blood in your poo, unexplained weight loss or a lasting change in bowel habits.
- Bowel preparation. Some preparations used before a colonoscopy contain magnesium citrate. The NHS says you will be given a laxative so your bowels are empty for the test. Follow the hospital’s instructions exactly; these are much larger amounts than any supplement.
We compare oxide, hydroxide, citrate and glycinate for constipation, with the trial evidence, in magnesium for constipation.
How much magnesium citrate should you take?
The key is the elemental magnesium: the actual magnesium in each dose, not the weight of the whole compound. Labels in the UK should show this, often as “magnesium” with a milligram figure and a % NRV (the NRV for magnesium is 375mg).
How much magnesium is in magnesium citrate?
It depends on which form of magnesium citrate the maker uses. We worked these out from the molecular weights, so treat them as approximate:
| Form | Magnesium content (approx.) | Magnesium in 1,000mg of the compound |
|---|---|---|
| Trimagnesium citrate, anhydrous (dry) | About 16% | About 160mg |
| Trimagnesium citrate, nonahydrate (contains water) | About 12% | About 120mg |
| Magnesium hydrogen citrate | About 11% | About 110mg |
So a capsule that says “1,000mg magnesium citrate” could give you anywhere from about 110mg to 160mg of magnesium. If the label only gives the compound weight, ask the brand.
How much do you need?
- The NHS says adults aged 19 to 64 need about 300mg a day (men) and 270mg a day (women), and most people can get this from food.
- Having 400mg or less a day from supplements is unlikely to cause any harm, according to the NHS.
- A sensible starting point for most adults is 100mg to 200mg of elemental magnesium a day, then adjust if your stomach is happy.
If you take more than one product, add up the magnesium in all of them, including multivitamins. For how long it takes to notice anything, see how long magnesium takes to work, and for what happens to it after you take it, how long magnesium stays in your body.
When to take magnesium citrate: morning or night?
There is no strong evidence that one time of day is better for absorption. What matters most is taking it consistently. A few practical points:
- With food if it upsets your stomach. Food slows things down and many people find it gentler.
- Split larger amounts into two smaller doses, morning and evening, to reduce the chance of loose stools.
- Evening suits people who build magnesium into a wind-down routine. If citrate loosens your stools, though, you may prefer it earlier in the day.
- Morning suits people who simply want to remember it with breakfast.
- Away from certain medicines: see the safety section below.
More detail by goal and form in the best time to take magnesium.
Magnesium citrate side effects
Most side effects come from the gut, and they are dose-related:
- Loose stools or diarrhoea, the most common one
- Tummy cramps or rumbling
- Wind and bloating
- Feeling sick, especially on an empty stomach
These usually settle if you lower the dose, take it with food or split it through the day. If they don’t, switch to a gentler form such as glycinate.
Much rarer is too much magnesium in the blood (hypermagnesaemia). It mainly happens when large amounts of magnesium laxatives are taken by people whose kidneys can’t clear magnesium properly. It can be serious, so get urgent medical help if you feel very weak, drowsy or unwell after taking a magnesium laxative. For all forms, see magnesium side effects.
Is magnesium citrate safe to take daily? Kidneys and medicines
For most healthy adults, a daily magnesium citrate supplement within the NHS guide of 400mg or less of magnesium from supplements is unlikely to cause harm. Using it every day as a laxative is different: speak to a GP or pharmacist rather than relying on it long term.
Kidneys
Your kidneys control how much magnesium your body keeps. If you have kidney disease or reduced kidney function, magnesium can build up, so don’t take magnesium supplements or laxatives unless your doctor advises it. Reviews of magnesium laxatives point to older adults and people with kidney impairment as the groups most at risk.
Medicines
Magnesium can bind to some medicines in the gut and reduce how much you absorb. Check with your pharmacist about timing if you take:
- Some antibiotics, such as doxycycline: the NHS lists antacids and indigestion treatments, many of which contain magnesium, among the things that may not mix well with it
- Levothyroxine for an underactive thyroid: the NHS lists antacids and calcium and iron supplements among the things that interact with it, and many antacids contain magnesium
- Bisphosphonates such as alendronic acid for osteoporosis: the NHS says to take it on an empty stomach, 30 minutes before breakfast and before any other medicines you swallow
A gap of a few hours usually avoids the problem, but the right gap varies by medicine, so check the leaflet in the pack.
Pregnancy, breastfeeding and children
Speak to your midwife, GP or pharmacist before taking any supplement during pregnancy or breastfeeding. We don’t recommend our products during pregnancy or breastfeeding, and all our products are for adults (18+) only. For background, see magnesium in pregnancy. Children should only take magnesium citrate, including as a laxative, on the advice of a GP or pharmacist.
Magnesium citrate vs glycinate
Both are well-absorbed, organic forms. The main difference is how they feel in your gut.
| Citrate | Glycinate (bisglycinate) | |
|---|---|---|
| Magnesium content | About 11 to 16% | About 14% |
| Absorption | Good | Good |
| Effect on the bowel | Mild to moderate, more at higher amounts | Low |
| Often chosen for | General top-up; people prone to constipation | Evening routines; sensitive stomachs |
Choose glycinate if other forms have upset your stomach or you want magnesium as part of a wind-down. Choose citrate if you tend towards sluggish bowels. Many people find a blend of the two a good balance. Our full side-by-side, including threonate, is in magnesium glycinate vs citrate vs threonate, and there is more on glycinate in our magnesium glycinate guide.
Magnesium citrate vs oxide: which is absorbed better?
Magnesium oxide is the cheapest form and is common in supermarket tablets. It holds a lot of magnesium by weight (about 60%), but less of it is absorbed. Two studies compared the forms directly:
- Lindberg and colleagues, 1990 (US). In the lab, magnesium oxide was virtually insoluble in water and only 43% soluble even in conditions mimicking peak stomach acid, while magnesium citrate was 55% soluble in plain water. In volunteers given the same amount of magnesium, the rise in urinary magnesium over 4 hours, a marker of how much was absorbed, was far higher after citrate than after oxide.
- Walker and colleagues, 2003 (University of Reading). In a 60-day randomised, double-blind, placebo-controlled trial, 46 healthy adults took 300mg of elemental magnesium a day as citrate, an amino acid chelate or oxide. Citrate gave the highest blood magnesium levels both after the first dose and after 60 days. Oxide was no different from placebo.
Both studies were small, but they point the same way: per milligram of magnesium, citrate is absorbed better than oxide. Oxide’s poor absorption is also why it has a stronger laxative effect and why it is widely used for constipation. For how these and other forms rank, see the best magnesium supplements in the UK.
Magnesium citrate powder vs tablets
The magnesium is the same; the format changes how easy it is to take.
- Powder dissolves into water or a warm drink, makes it easy to adjust the amount and avoids swallowing large tablets. Citrate is a bulky compound, so a meaningful dose can take up a lot of space.
- Tablets and capsules are convenient and tasteless, but you may need two or more a day to reach a useful amount of elemental magnesium.
- Liquids and drinks are absorbed in a similar way to powder once mixed.
Choose the one you’ll take every day. More in magnesium powder vs tablets.
Why our complex uses citrate and glycinate together
Our Magnesium Glycinate Sleep Complex combines magnesium bisglycinate with magnesium citrate, giving 148mg of elemental magnesium per serving, well within the NHS guide for supplements. We use both because glycinate is gentle on the stomach and citrate is a well-absorbed form, so you get a useful amount of magnesium in an easy daily drink. It is a berry-flavoured powder you stir into water as part of an evening routine, with glycine, L-theanine, chamomile, passionflower, hops and oat straw. It is designed as a gentle evening drink, not a laxative.
Magnesium contributes to the reduction of tiredness and fatigue, normal functioning of the nervous system and normal psychological function. It’s vegan, made in the UK and third-party lab tested.
Related guides
- See how citrate compares with magnesium malate.
- For the other side of the comparison, read magnesium oxide vs citrate vs glycinate.
- Does magnesium make you poop or sleep?
FAQs
Is magnesium citrate a laxative?
It can be. Unabsorbed magnesium citrate draws water into the bowel and softens stools. At everyday supplement amounts the effect is usually mild; at higher amounts it is stronger. Ask a pharmacist before using it as a laxative.
Is it safe to take magnesium citrate every day?
For most healthy adults, yes, within the NHS guide of 400mg or less of magnesium a day from supplements. Check with a GP first if you have kidney problems or take regular medicines, and don’t use it daily as a laxative without advice.
How much magnesium is in magnesium citrate?
Roughly 11 to 16% by weight, depending on the form. So 1,000mg of magnesium citrate gives about 110mg to 160mg of magnesium. Check the label for the elemental figure.
Is magnesium citrate or glycinate better?
Both are well absorbed. Citrate has more of a loosening effect on the bowel; glycinate is gentler on the stomach and more often chosen for evenings. A blend gives you some of each.
Is magnesium citrate good for sleep?
No magnesium form has an authorised sleep claim, and the research on magnesium and sleep is mixed. Magnesium contributes to normal functioning of the nervous system. Glycinate is the more common bedtime choice because citrate can loosen stools.
Can I take magnesium citrate with other medicines?
Magnesium can reduce the absorption of some antibiotics, levothyroxine and bisphosphonates such as alendronic acid. Leave a gap of a few hours and ask your pharmacist for the right timing.
Sources
- NHS. Vitamins and minerals: others (magnesium).
- NHS. Laxatives.
- NHS. Colonoscopy.
- NHS. Levothyroxine, doxycycline and how and when to take alendronic acid.
- Lindberg JS et al. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr, 1990. PMID 2407766.
- Walker AF et al. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res, 2003. PMID 14596323.
- Garrison SR et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev, 2020. PMID 32956536.
- Mori H et al. Magnesium oxide in constipation. Nutrients, 2021. PMID 33525523.
- William JH et al. Magnesium and drugs commonly used in chronic kidney disease. Adv Chronic Kidney Dis, 2018. PMID 29793666.
This guide is general information, not medical advice. Evopure makes the Magnesium Glycinate Sleep Complex.
