Magnesium citrate: benefits, dosage, constipation and how it compares with glycinate

What magnesium citrate is

Magnesium citrate is a salt of magnesium and citric acid. It dissolves well in water, so it comes as capsules, tablets and powders to mix into a drink. Forms that dissolve well tend to be absorbed more completely, and small studies suggest citrate is absorbed better than magnesium oxide.

Magnesium makes up only part of the compound’s weight:

• about 16% in anhydrous magnesium citrate;
• about 11–12% in hydrated forms.

On labels, the anhydrous salt may appear as trimagnesium citrate or magnesium citrate anhydrous, and the hydrate as magnesium citrate nonahydrate. If the form isn’t stated, assume the lower figure.

So “magnesium citrate 1,000 mg” means roughly 110–160 mg of actual magnesium. Reputable brands list elemental magnesium in the Supplement Facts panel, with the form in brackets: “Magnesium (as magnesium citrate) 200 mg”. That’s the number to go by. For how citrate compares with every other form, see types of magnesium compared.

Magnesium citrate benefits: what it’s good for

Magnesium helps turn food into energy and supports normal muscle and nerve function. The NHS says adults aged 19–64 need 300 mg a day (men) and 270 mg (women); EFSA’s figures are 350 mg and 300 mg. Most of that should come from food.

Citrate makes sense if:

• you eat few nuts, seeds, beans and wholegrains;
• you’ve taken proton pump inhibitors (such as omeprazole) or diuretics for a long time, which increase magnesium losses;
• you’re prone to constipation and a mild laxative effect would help;
• you want an affordable form and don’t need glycinate for tolerability.

What not to expect: a noticeable effect on sleep, stress or energy if you already get enough magnesium. The evidence for magnesium and sleep is modest; our guide to sleep supplements covers it. Who is actually at risk, and why a blood test says little, is explained in magnesium deficiency symptoms.

Magnesium citrate for constipation

Magnesium salts are classic osmotic laxatives. Magnesium that isn’t absorbed draws water into the bowel and makes it move more. So looser stools on citrate aren’t an allergy or a sign of poor quality: they’re an expected effect of the dose.

Keep three things in mind:

• Laxative doses are higher than supplement doses. Magnesium laxatives contain several times more than a daily supplement, above the supplement upper limit.
• Short-term only. The NHS advises using laxatives for a short time; most start working within 3 days.
• Food and fluids first. Fibre, plenty of water and regular activity are the first steps for constipation.

See a GP if:

• constipation isn’t improving with treatment or keeps coming back;
• there’s blood in your poo;
• you’re losing weight without trying or feel tired all the time;
• you’re often bloated or have tummy pain;
• your bowel habits have suddenly changed.

Magnesium citrate dosage and timing

• Take it with food to reduce stomach upset.
• Keep each dose to 200 mg or less. Larger single doses are more likely to loosen stools, and the NHS notes that more than 400 mg for a short time can cause diarrhoea.
• Time of day barely affects absorption. If citrate affects your bowels, morning or daytime is easier.
• Stir powder into a glass of water and drink it straight away.
• Add in magnesium from multivitamins, electrolyte drinks and effervescent tablets.

Work out how much magnesium your product gives you a day:

Magnesium citrate powder vs capsules

Powder suits you if you struggle to swallow capsules or want to find your dose gradually. Start with half a serving for a few days and increase only if your stools stay normal. Capsules are easier for the same dose every day: open the tub, take two, done.

Step by step, it looks like this:

Magnesium citrate vs glycinate

There are almost no human trials comparing the absorption of citrate and glycinate directly, so choose by tolerability and purpose.

If citrate gives you loose stools even at 100–200 mg, switch to magnesium glycinate. If you take a magnesium product with added vitamin B6, check the B6 dose: see magnesium and vitamin B6.

Side effects, who should avoid it and interactions

The most common side effects of magnesium supplements are loose stools, nausea and stomach cramps. EFSA’s 250 mg limit for supplements is based on mild diarrhoea. Serious magnesium excess is rare and usually linked to very large doses of laxatives or antacids, or to kidney disease.

Get medical advice before taking it if you:

• have kidney disease;
• take tetracycline or quinolone antibiotics: take the antibiotic at least 2 hours before or 4–6 hours after magnesium;
• take bisphosphonates for osteoporosis: separate by at least 2 hours;
• are pregnant or breastfeeding;
• want to give magnesium to a child: doses depend on age and weight, so ask a paediatrician.

Our vitamin compatibility chart shows which other supplements to keep apart. Severe diarrhoea, weakness or an irregular heartbeat mean you should stop and get medical advice.

How to choose magnesium citrate on iHerb

1. Decide on the format: capsules for a fixed dose, powder for a flexible one.
2. Find elemental magnesium per serving in the Supplement Facts and check how many capsules or scoops that serving is.
3. Pick a strength that gives 100–200 mg of magnesium a day and keeps you within 250 mg from supplements.
4. In powders, check for sugar, sweeteners and flavourings.
5. Compare the price per 100 mg of elemental magnesium in £ or €, not per tub.

For telling compound weight from elemental magnesium, see our Supplement Facts guide.