Magnesium for Bloating: Does It Help and Which Type Is Best?

Does magnesium help with bloating?

It depends on what is causing your bloating. The NHS says the most common reason is a lot of gas in your gut, from certain foods, fizzy drinks or swallowing air. Bloating can also come from constipation, a food intolerance, coeliac disease, irritable bowel syndrome (IBS) or your period.

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Magnesium is only relevant to a couple of those causes, and the research is mostly about constipation rather than bloating itself:

• Bloating from constipation. In a 2021 Japanese trial of 90 adults with long-term constipation, 68% of those taking magnesium oxide for four weeks reported overall improvement, compared with 12% on a placebo. A smaller 2019 trial in 34 women found a similar pattern: 71% improved on magnesium oxide against 25% on placebo, with softer stools and faster transit through the gut.
• Magnesium-rich mineral water. In a French trial of 244 women with constipation, drinking a litre a day of a magnesium and sulfate-rich mineral water reduced constipation in more women than low-mineral water by week two. The trial was run with the water’s maker.
• Bloating before a period. A small University of Reading trial found 200mg of magnesium a day reduced premenstrual fluid retention symptoms, including abdominal bloating, by the second cycle.

What the research does not show: few trials have measured bloating as their main outcome, and we found no good evidence that magnesium eases bloating caused by trapped wind, food intolerances or a large meal. In those cases, changes to what and how you eat usually make more difference.

One honest catch: the constipation trials used 1.5g of magnesium oxide a day, which is roughly 900mg of magnesium. That is more than double the 400mg a day the NHS says is unlikely to cause harm from supplements, so treat those doses as medicine, used with a pharmacist’s or GP’s advice.

Comparing brands and forms? Our best magnesium supplement UK guide sets out what to look for on the label, form by form.

For the full picture on bowels, see magnesium for constipation, and for wider gut habits, how to improve gut health.

How magnesium works in the gut

Magnesium affects your gut in three main ways:

• It draws water into the bowel. Poorly absorbed forms such as citrate, oxide and sulfate stay in the gut and pull water in, which softens stools. This is how osmotic laxatives work, and why magnesium can matter when bloating comes from being backed up.
• It neutralises stomach acid. Some magnesium compounds, such as magnesium hydroxide and carbonate, are used in antacids for indigestion and heartburn.
• It is part of normal muscle function. Magnesium contributes to normal muscle function. That is an authorised claim for magnesium in general, not evidence that it eases bloating, and no good trials show that it does.

The form matters more than the total amount here. A well-absorbed form leaves less magnesium in the bowel to draw water, so it has less effect on stools either way. Our guide to the types of magnesium compares every form.

How much water should you drink a day? Our guide gives the NHS guidance and simple signs you are getting enough.

Which magnesium is best for bloating?

Start with the likely cause of your bloating, then choose the form that suits it.

For bloating with constipation, citrate is the usual first choice because it works more gently than oxide. Read more in our guides to magnesium citrate and magnesium oxide. If your gut is sensitive and you want magnesium for other reasons, such as tiredness or an evening routine, glycinate is less likely to upset your stomach.

iOur Magnesium Glycinate Sleep Complex combines bisglycinate with citrate and gives 290mg of magnesium per serving. It is designed as an evening drink rather than a laxative, so if constipation is your main problem, speak to a pharmacist about a proper laxative.

Magnesium glycinate vs citrate for bloating

This is the most common question we get on this topic, and the answer depends on what your stools are doing.

• Choose citrate if you are bloated because you are constipated. Its osmotic effect is the point.
• Choose glycinate if you are not constipated, have loose stools or IBS with diarrhoea, or found citrate gave you wind. Glycinate is bound to the amino acid glycine and has little laxative effect at usual doses.
• A blend of both sits in between. Small amounts of citrate are unlikely to loosen stools much for most people, but start low if your gut is sensitive.

Neither form is a treatment for bloating itself. For a side-by-side look at absorption and uses, see magnesium glycinate vs citrate vs threonate.

How much magnesium to take for bloating, and when

The NHS says adults need 300mg (men) or 270mg (women) of magnesium a day, and that most people can get this from a varied diet. Having 400mg or less a day from supplements is unlikely to cause harm, while high doses of more than 400mg for a short time can cause diarrhoea.

• Start low: around 100 to 200mg of elemental magnesium a day, and increase slowly if needed. The figure that counts is the magnesium content, not the weight of the whole compound.
• Count everything: antacids and laxatives that contain magnesium count towards your total.
• Drink enough: the NHS advises plenty of fluids with osmotic laxatives, to avoid dehydration.
• Timing: there is no strong evidence that morning or evening is better for bloating. Taking it with food is kinder to the stomach, and many people use citrate in the evening. See the best time to take magnesium for more.

Food counts too: nuts, seeds, wholegrains and leafy greens are good sources, and many are high in fibre. Our list of foods high in magnesium has amounts per portion.

How quickly does magnesium work for bloating?

It depends on the cause, and it is slower than many people expect:

If you bought a laxative without a prescription, the NHS advises stopping once your constipation improves, not using it for longer than 7 days, and speaking to a doctor or pharmacist if it has not helped after 3 days. More detail in how long magnesium takes to work.

Can magnesium cause bloating?

Yes, sometimes. The NHS lists farting, bloating, stomach cramps and diarrhoea among the common side effects of most laxatives, and magnesium in higher doses works like one. Too much magnesium, or a sudden large dose, can leave you windier and more bloated than before. People with IBS or a sensitive gut are more likely to notice it.

If magnesium seems to make you bloated:

• lower the dose or split it across the day
• take it with food
• switch from citrate or oxide to glycinate, which is gentler
• check whether you are also taking an antacid or laxative that contains magnesium
• speak to a pharmacist if it carries on

Magnesium has no calories, so it does not cause fat gain. Feeling heavier or puffy after starting it is more likely to be wind or a fuller bowel. Our magnesium side effects guide covers the rest, including who should take extra care.

Bloating before your period

Premenstrual bloating is one of the most common reasons women try magnesium. In the University of Reading trial, 38 women took 200mg of magnesium (as oxide) or a placebo every day for two cycles. There was no difference in the first month, but in the second month the magnesium group had fewer fluid retention symptoms: weight gain, swollen hands and feet, breast tenderness and abdominal bloating.

That is one small study of mild symptoms, so treat it as promising rather than proven. A 2019 review of 13 observational studies found no clear link overall between blood magnesium levels and PMS, and its authors called for better trials.

If your bloating is more puffiness and swelling than a tight, gassy stomach, our guide to magnesium for water retention goes into more detail. Magnesium for PMS covers cramps and mood too. Bloating that happens most days, not just before your period, needs a GP check (see below).

Magnesium, IBS and bloating

Bloating is one of the core symptoms of IBS. The NICE guideline for IBS in adults lists abdominal bloating, distension, tension or hardness among the features doctors look for, and notes it is more common in women than men.

NICE does not name magnesium specifically, but it does say:

• laxatives should be considered for constipation in IBS, but people should be discouraged from taking lactulose
• laxative doses should be adjusted to aim for a soft, well-formed stool
• people with wind and bloating may find oats and linseeds (up to 1 tablespoon a day) helpful
• anyone who tries probiotics should take them for at least 4 weeks while watching the effect
• diets such as low FODMAP should only be given by a healthcare professional with expertise in diet

So if your IBS leans towards constipation, osmotic magnesium is one option to discuss with your GP or pharmacist. If it leans towards diarrhoea, citrate and oxide are likely to make things worse. More on gut options in the best supplements for digestion and probiotics and bloating.

Who should check with a pharmacist or GP first

The NHS advises checking with a pharmacist or doctor before using laxatives if you:

• are pregnant or breastfeeding
• have a heart condition, such as heart failure
• have a digestive condition, such as Crohn’s disease or ulcerative colitis
• are taking opioid painkillers, such as codeine or morphine

We would add kidney disease and any regular prescription medicine to that list. We don’t recommend our products during pregnancy or breastfeeding, and they are for adults only.

Other ways to reduce bloating

For most bloating, everyday habits make more difference than any supplement. The NHS suggests:

• Eat smaller, more frequent meals, and avoid large meals late at night.
• Chew with your mouth closed so you swallow less air, and don’t slouch when eating.
• Cut back on fizzy drinks, alcohol and caffeine.
• Go easy on foods known to cause gas, such as cabbage, beans and lentils.
• Exercise regularly: it helps digestion and can ease bloating when you already feel it.
• Drink plenty of water, and if you are constipated, eat foods high in soluble fibre such as oats or linseed. Add fibre gradually: see how to eat more fibre without bloating.
• Massage your stomach from right to left to help release trapped wind.
• Ask a pharmacist about simeticone for wind, or a laxative for constipation.

iA food diary helps you spot your own triggers. If you suspect a food intolerance or coeliac disease, speak to a GP before cutting out whole food groups.

Foods that commonly cause bloating

Some foods are harder to digest and make more gas in your gut. The NHS lists these as foods and drinks that can make you fart:

• cabbage, broccoli, cauliflower and brussels sprouts
• pulses, such as beans and lentils
• onions
• dried fruit, such as raisins and apricots
• food or drinks containing the sweetener sorbitol, which is used in some sugar-free sweets and chewing gum
• fizzy drinks and beer

The NHS also suggests not eating lots of processed, sugary, spicy or fatty foods, and avoiding any food you know you are intolerant to. Many of the foods on the list are good for you, so cut back on the ones that bother you rather than dropping them all.

If you have IBS, NICE says diets that exclude foods, such as the low FODMAP diet (which limits certain fermentable carbohydrates), should only be given by a healthcare professional with expertise in diet. If simple changes aren’t working, a GP can refer you to an NHS dietitian.

When to see a GP about bloating

Most bloating is harmless, but don’t use supplements to mask bloating that keeps coming back. The NHS advises seeing a GP if:

• you feel bloated regularly
• you have changed your diet but keep feeling bloated
• you have bloating and unintentional weight loss
• you have bloating and blood in your poo

iAsk for an urgent GP appointment or call 111 if you have bloating with vomiting, diarrhoea or constipation, a stomach ache, a high temperature, a swelling or lump in your tummy, acid reflux, or you cannot pee, poo or fart.

Call 999 or go to A&E if you have a swollen stomach with severe stomach pain that came on suddenly, you are vomiting blood or your vomit looks like ground coffee, or you have severe difficulty breathing.

Related guides

• If bloating comes with heartburn or a sour taste, see acid reflux symptoms and causes.
• Foods and drinks that help constipation.
• Easing period cramps: painkillers, heat and more.
• Not sure if your bloating is IBS? See IBS: symptoms and how to know you have it.
• Feeling less bloated is different from losing fat, as our guide to magnesium for weight loss explains.
• How much magnesium per day is too much.