Magnesium for Water Retention and Swollen Feet: Does It Help? (UK)

Does magnesium help with water retention?

Water retention, or oedema, is when fluid builds up in the body’s tissues, usually in the feet, ankles, legs, hands or face. The clearest evidence for magnesium is for the kind many women get before their period.

Taking magnesium in the evening? Our guide to magnesium for sleep covers which form to choose and how much the studies used.

Stocking up for winter? Our Black Friday supplement deals run from 27 to 30 November.

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In a trial at the University of Reading, 38 women took 200mg of magnesium or a placebo every day for two menstrual cycles. There was no difference in the first month, but in the second month the magnesium group had fewer fluid retention symptoms: less weight gain, less swelling of the hands and feet, less breast tenderness and less abdominal bloating.

For water retention with other causes, such as hot weather or long periods of standing, there is little direct research on magnesium. It plays a part in keeping your body’s fluid and mineral balance steady, so topping up a low intake makes sense, but it is not a proven fix.

Read more: magnesium for bloating and magnesium for PMS

Does magnesium cause water retention?

There is no good evidence that magnesium supplements make you retain water. If anything, forms such as citrate draw water into the bowel and can loosen stools, which is the opposite effect. If you notice swelling after starting any supplement, stop it and speak to a pharmacist, as something else may be going on.

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

Best magnesium for water retention

No single form has been proven best for water retention. The trial above used magnesium oxide, but better-absorbed forms are a sensible choice for everyday use.

Our Magnesium Glycinate Sleep Complex combines bisglycinate and citrate, giving 290mg of magnesium per serving as an evening drink. For every form side by side, see our guide to the types of magnesium or magnesium glycinate vs other forms.

How much magnesium to take for water retention, and how long it takes

Most studies on fluid retention used 200 to 400mg of magnesium a day. The NHS says adults need 300mg (men) or 270mg (women) a day, mostly from food, and that 400mg or less a day from supplements is unlikely to cause harm. Higher doses can cause diarrhoea.

• Check the elemental amount on the label, not the weight of the compound.
• Give it time. In the Reading trial, the benefit appeared in the second month, so try it for at least two cycles.
• Take it daily. Your body clears extra magnesium within a day or two, so consistency matters.

Read more: how long magnesium takes to work and the best time to take magnesium

Magnesium for swollen feet and ankles: causes and what helps

Mild swelling in both ankles or feet is common and often harmless. Everyday causes include standing or sitting for a long time, hot weather, eating a lot of salty food, periods, pregnancy and some medicines. If you are pregnant, read our guide to magnesium in pregnancy and speak to your midwife before taking supplements.

The NHS suggests these simple steps to ease swelling:

• raise your legs on a chair or pillows when you can
• get some gentle exercise, such as walking, to help your circulation
• wear wide, comfortable shoes with a low heel and soft sole
• wash, dry and moisturise your feet
• avoid standing or sitting for long periods, and avoid tight socks, clothes or shoes

Magnesium creams, sprays and oils are popular for tired legs and feet. There is little evidence that much magnesium is absorbed through the skin, but the massage itself and raising your feet afterwards can help you feel more comfortable.

How to get rid of water retention

Most mild water retention settles on its own. The NHS suggests:

• Raise your legs on a chair or pillows when you can.
• Move regularly: gentle exercise such as walking helps blood flow.
• Don’t stand or sit still for long periods. On long journeys, get up and walk about.
• Avoid tight clothes, socks and shoes; wear wide, comfortable shoes with a low heel.
• Cut down on salt. Adults should have no more than 6g a day, about a level teaspoon, and much of it is hidden in bread, ready meals and takeaways.

See electrolytes and magnesium for bloating.

Water retention vs fat: how to tell

Do water retention tablets work?

Prescription “water tablets” (diuretics) are medicines for conditions such as heart failure and high blood pressure, and should only be taken if a doctor prescribes them. Over-the-counter herbal water retention products are usually traditional herbal remedies with little good evidence behind them. Don’t use either to lose weight: water weight comes straight back, and losing too much fluid can upset your body’s salt balance. If you have ongoing swelling, see your GP to find the cause.

When swelling needs a doctor

Supplements are not the answer for every kind of swelling. The NHS advises:

• See a GP if both ankles, feet or legs are swollen and it has not improved after a few days of home treatment, it is getting worse, or you have a heart, kidney or leg vein condition.
• Get an urgent GP appointment or call 111 if only one ankle, foot or leg is swollen and you don’t know why, the swelling follows an injury, or it is severe, painful or getting worse.
• Call 999 if swelling comes with shortness of breath, a tight, heavy or painful chest, coughing up blood, palpitations, or feeling faint or clammy. This could be a blood clot in the lungs.

How to choose a quality magnesium supplement

• Choose brands that publish third-party lab reports for every batch.
• Check the elemental magnesium per serving, not just the compound weight.
• Pick a well-absorbed form such as citrate or glycinate.
• Look for vegan, non-GMO products without unnecessary fillers.
• Count magnesium from every product you take, including multivitamins and antacids, and stay at 400mg or less a day from supplements.

Related guides

• PMS symptoms.
• See how much water you should drink a day.
• Our guide to period pain relief.
• Losing water is not the same as losing fat: see does magnesium help you lose weight?
• Read more about magnesium glycinate, including how to read the elemental magnesium on the label.