Why magnesium comes in different forms
Magnesium is a mineral involved in hundreds of reactions in the body, including muscle and nerve function, energy production, blood sugar control and bone health. Adults need roughly 310 to 420 mg a day, mostly from foods such as nuts, seeds, whole grains, legumes and green leafy vegetables.
Supplements bind magnesium to another molecule, a salt or an amino acid, so it can be packaged and absorbed. That partner molecule affects how much elemental magnesium each capsule contains, how well it is absorbed and how it behaves in the gut.
Magnesium citrate
- Magnesium bound to citric acid; dissolves well and is well absorbed.
- At higher doses, unabsorbed magnesium draws water into the bowel and softens stools.
- Available as capsules, powders and as an oral liquid laxative.
- Useful for occasional constipation and when a mild laxative effect is welcome.
- More likely than glycinate to cause cramps or diarrhoea.
As a laxative, the liquid works within hours; see how long magnesium citrate takes to work.
Magnesium glycinate
- Magnesium bound to glycine (bisglycinate); well absorbed and gentle on the stomach.
- Much less likely to cause loose stools, so it is easier to take daily.
- Popular for sleep and relaxation, although evidence for these effects is limited.
- Often slightly more expensive than citrate.
- Capsules can be large because glycine adds bulk.
For a comparison with another form, see magnesium threonate vs glycinate.
Side-by-side comparison
- Absorption: both are considered well absorbed, better than magnesium oxide.
- Effect on the bowel: citrate has a laxative effect; glycinate rarely does.
- Best for constipation: citrate.
- Best for daily use with a sensitive gut: glycinate.
- Sleep and stress: glycinate is the usual practical choice; benefits are most likely if intake was low.
- Cost: citrate is usually cheaper.
How much to take
Check the label for the amount of elemental magnesium, not the weight of the whole compound. Typical supplement doses are 100 to 350 mg of elemental magnesium a day, often taken with food. Splitting the dose can reduce stomach upset.
In the US, the upper limit for magnesium from supplements in adults is 350 mg a day; the NHS advises that 400 mg a day or less from supplements is unlikely to cause harm. Magnesium from food does not count towards these limits, because the kidneys remove the excess in healthy people.
Getting magnesium from food
Most people can meet their needs with food. Good sources include pumpkin seeds, almonds, cashews, spinach, black beans, edamame, wholegrain bread, oats, brown rice, dark chocolate and some mineral waters.
A supplement makes more sense if your diet is limited, if you take medicines that lower magnesium, such as long-term proton pump inhibitors or some diuretics, or if a blood test shows low levels. See drinks high in magnesium.
Who should be careful
- Kidney disease: magnesium can build up; do not take supplements without medical advice.
- Medicines: magnesium reduces absorption of some antibiotics (tetracyclines and quinolones) and osteoporosis medicines (bisphosphonates); take them at least 2 hours apart.
- Heart rhythm and blood pressure medicines: check with your doctor or pharmacist.
- Pregnancy and breastfeeding: ask a professional before starting a supplement.
- Too much: diarrhoea, nausea and cramps are early signs; very high doses can be dangerous.
Which one should you choose?
If your main goal is to relieve occasional constipation, magnesium citrate is the better fit. If you want a daily magnesium supplement without affecting your bowel, or you are taking it hoping to sleep better, magnesium glycinate is usually more comfortable.
Neither replaces treatment for an underlying problem. Ongoing constipation, poor sleep or muscle cramps deserve an assessment of diet, habits and possible causes; see food for constipation.
Key points to remember
- Both forms are well absorbed; citrate has a laxative effect and glycinate is gentle.
- Choose citrate for constipation and glycinate for daily use or a sensitive gut.
- Keep supplements to 350 mg of elemental magnesium a day unless advised otherwise.
- People with kidney disease or on interacting medicines should ask first.
Questions about magnesium citrate and glycinate
These answers are general information and do not replace an examination or individual medical advice.
Is magnesium citrate or glycinate better for sleep?
Glycinate is the usual choice because it is gentle on the gut. Evidence for sleep benefits is limited and strongest when intake was low.
Is magnesium citrate or glycinate better for constipation?
Citrate, because it draws water into the bowel and softens stools.
Can I take magnesium citrate and glycinate together?
Yes, but keep the total from supplements within 350 mg of elemental magnesium a day unless advised otherwise.
Which magnesium is best absorbed?
Citrate and glycinate are both well absorbed, better than magnesium oxide.
Does magnesium glycinate cause diarrhoea?
It can at high doses, but much less often than citrate.
When is the best time to take magnesium?
Any time that suits you, ideally with food. Many people take glycinate in the evening.
Sources
- NIH Office of Dietary Supplements · Magnesium fact sheet
- NHS · Vitamins and minerals: others (magnesium)
- MedlinePlus (NIH) · Magnesium citrate drug information
This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.