Magnesium Bisglycinate vs Citrate vs Oxide: Which Form Should You Choose?

Pick up three magnesium supplements in a pharmacy and you may find three different compounds: oxide, citrate and bisglycinate (often sold as glycinate), with malate, threonate and others close by. The label number that looks biggest isn't always the one that matters, and the form changes how the supplement feels to take.

This guide compares the common forms, explains how to read a magnesium label, and helps you choose.

First, what magnesium does

Magnesium is involved in hundreds of enzyme reactions. It contributes to the reduction of tiredness and fatigue, normal energy-yielding metabolism, normal functioning of the nervous system, normal muscle function, normal psychological function, electrolyte balance, and the maintenance of normal bones and teeth.

Good food sources include pumpkin and other seeds, nuts, beans and lentils, whole grains, leafy greens and dark chocolate. Diets built around refined foods are often low in magnesium, which is why it is a common supplement.

How to read a magnesium label

Every magnesium supplement is magnesium bonded to another molecule. Labels may list the weight of the whole compound or just the elemental magnesium, the magnesium itself. Elemental magnesium is the figure to compare. For example, 1,000 mg of magnesium bisglycinate provides roughly 140 mg of elemental magnesium, because glycine makes up most of the weight.

The EU reference intake for adults is 375 mg of magnesium a day from all sources. The European Food Safety Authority sets an upper limit of 250 mg a day for magnesium taken as supplements, mainly because higher doses can loosen the bowels.

Magnesium oxide

What it is: magnesium bonded to oxygen. It's cheap and very dense, so a small tablet can list a large amount of magnesium.

The catch: it doesn't dissolve well, and studies comparing forms have found it is absorbed less than more soluble forms. One small study measured fractional absorption of oxide at only around 4%. The unabsorbed magnesium stays in the gut and draws in water, which is why oxide is used as a laxative and antacid.

Best for: occasional constipation or indigestion, as directed. Less suited as a daily magnesium top-up.

Magnesium citrate

What it is: magnesium bonded to citric acid. It dissolves well and is absorbed better than oxide in comparative studies.

The catch: at higher doses it can still have a laxative effect, which some people welcome and others don't.

Best for: a good-value general option, particularly for people who also want a gentle effect on bowel regularity.

Magnesium bisglycinate (glycinate)

What it is: magnesium bonded to two molecules of the amino acid glycine, a so-called chelate. The glycine bond keeps the magnesium in a soluble form, and chelates can be absorbed through amino acid pathways as well as the usual mineral channels.

Why people choose it: it is widely reported to be gentle on the stomach, with less of the laxative effect seen with oxide or citrate. That makes it easier to take daily at a meaningful dose. Glycine is itself an amino acid the body uses in many processes.

The catch: glycinate tablets and capsules are bulkier for the same elemental magnesium, and it costs more than oxide.

Best for: daily, long-term supplementation, especially for anyone with a sensitive stomach.

Other forms you'll see

• Malate: bonded to malic acid. Well absorbed and generally well tolerated; often marketed for daytime use.
• Threonate (L-threonate): a newer form marketed for brain health. Interesting early research, but much less human evidence and usually a low magnesium content per capsule.
• Chloride and lactate: soluble forms used in some products and in topical sprays. Evidence that magnesium sprays or bath salts raise levels through the skin is weak.
• Taurate: bonded to the amino acid taurine; less studied.

Quick comparison

• Oxide: lowest cost, high magnesium per tablet, lower absorption, most likely to loosen bowels.
• Citrate: good absorption, good value, can loosen bowels at higher doses.
• Bisglycinate: good absorption, gentlest on the stomach, bulkier and costs more.
• Malate: good absorption, well tolerated, fewer studies.

How to take magnesium well

• Split the dose if you take more than about 200 mg; smaller amounts are absorbed more efficiently and are easier on the gut.
• Take it with food if it upsets your stomach.
• Pick a time you'll stick to. Many people prefer the evening; consistency matters more than timing.
• Keep it apart from certain medicines. Magnesium can reduce absorption of some antibiotics (tetracyclines and quinolones), bisphosphonates for osteoporosis and levothyroxine. Leave a gap of a few hours, and ask your pharmacist.
• Space it from iron and zinc if you take them, as minerals compete for absorption.

Who should check first

People with kidney disease should not take magnesium supplements without medical advice, because the kidneys clear excess magnesium. If you take prescribed medicines, are pregnant or breastfeeding, check with your GP or pharmacist.

Key takeaways

• Compare elemental magnesium, not the total compound weight.
• Oxide is cheap and dense but less well absorbed and more likely to loosen bowels.
• Citrate is a good-value, well-absorbed option.
• Bisglycinate is well absorbed and the gentlest on the stomach, which suits daily use.
• Stay within 250 mg a day of supplemental magnesium unless advised otherwise, and check medicine interactions.

Our NeuroThrive™ Magnesium Bisglycinate uses the chelated bisglycinate form in a vegan capsule.

Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. This article is for general information and is not medical advice.