# Types of magnesium compared: which form should you take?

Source: https://magnesiumguide.uk/forms/
Author: Nell Hartley · Updated 2026-11-04

**Short answer:** For most people, magnesium citrate or glycinate is a sensible choice: both are reasonably well absorbed, and glycinate is the gentlest on the gut. Magnesium oxide holds the most magnesium per tablet but is poorly absorbed and acts as a laxative. Pricier forms such as L-threonate have little independent evidence behind their claims.

## Why are there so many forms?

Magnesium on its own is a reactive metal, so supplements bind it to something else: an acid (citrate, malate, threonate), an amino acid (glycinate, taurate), or a simple mineral partner (oxide, carbonate, chloride, sulphate). The partner changes three things:

1. **How much magnesium is in each capsule.** Oxide is 60% magnesium by weight; glycinate is about 14%; L-threonate about 8%.
2. **How well it dissolves and is absorbed.** Forms that dissolve easily, such as citrate and chloride, tend to be absorbed better than oxide.
3. **How it affects your gut.** Unabsorbed magnesium draws water into the bowel. That makes oxide and sulphate useful laxatives, and gentle forms such as glycinate easier to take at higher doses.

## How do the main forms compare?

| Form | Magnesium by weight | Absorption | Gut | Price per 100 mg magnesium |
| --- | --- | --- | --- | --- |
| [Oxide](/forms/magnesium-oxide/) | 60% | Low | Laxative | Lowest |
| [Citrate](/forms/magnesium-citrate/) | 16% | Good | Can loosen stools | Low |
| [Glycinate](/forms/magnesium-glycinate/) | 14% | Good | Gentle | Medium |
| Malate | 15% | Probably good, little data | Gentle | Medium |
| Chloride | 12% | Good | Can loosen stools | Low to medium |
| [Sulphate (Epsom salt)](/forms/epsom-salts-and-sprays/) | 10% | Used for baths and as a laxative | Strong laxative by mouth | Low |
| Taurate | 9% | Little data | Gentle | High |
| [L-threonate](/forms/magnesium-l-threonate/) | 8% | Little human data | Gentle | Highest |

## What do absorption studies show?

Only a handful of studies compare forms directly, and they are small:

- A 2001 US study found magnesium oxide was poorly absorbed (about 4%), while chloride, lactate and aspartate were absorbed equally well and better than oxide.
- A 2003 University of Reading trial in 46 healthy people gave 300 mg of magnesium a day for 60 days as citrate, an amino acid chelate or oxide. Citrate and the chelate were absorbed better than oxide, and citrate raised blood levels the most. Oxide did no better than placebo.
- A 1994 study in 12 people who had part of their small bowel removed found glycinate and oxide were absorbed about equally overall, but glycinate did better in the four people who absorbed least, and caused fewer gut problems.

These are short studies of how much reaches the blood or urine. They don't show that one form works better for sleep, migraine or anything else, and no trial has compared forms on those outcomes.

## Which form for which purpose?

- **Topping up a low intake:** [citrate](/forms/magnesium-citrate/) or [glycinate](/forms/magnesium-glycinate/).
- **Sensitive stomach, or higher doses:** glycinate.
- **Constipation:** [oxide](/forms/magnesium-oxide/) or a licensed laxative.
- **Migraine prevention:** the best trial used citrate at about 600 mg a day, after advice from a GP. See [migraine](/benefits/migraine/).
- **Sleep:** placebo-controlled trials used oxide, bisglycinate and L-threonate; none has been shown better than another. See [sleep](/benefits/sleep/).
- **Baths and sprays:** unlikely to raise your magnesium at all. See [Epsom salts and sprays](/forms/epsom-salts-and-sprays/).

## How do you read the label?

Look for the **elemental magnesium** per serving, often in the nutrition table, and check whether the serving is one capsule or several. Ignore the big number on the front if it is the compound weight. Our [buying guide](/buying-guide/) has a calculator that works out the real cost per 100 mg.

## Frequently asked questions

### What is the best form of magnesium?

There is no single best form. Citrate and glycinate are good all-rounders. Oxide is best kept for constipation. If a form upsets your stomach, switch to glycinate or take smaller doses with food.

### Is magnesium glycinate better than citrate?

Neither has been clearly shown to work better for sleep, cramps or anything else. Citrate is cheaper and well studied for absorption; glycinate is less likely to loosen stools. Choose by price and how your gut reacts.

### What does elemental magnesium mean?

It is the weight of the magnesium itself, without the compound it is bound to. A 500 mg capsule of magnesium citrate contains only about 80 mg of elemental magnesium. Dose advice and the NHS 400 mg limit refer to elemental magnesium.

### Can you take two forms of magnesium together?

Yes. Many products combine forms. What matters is the total elemental magnesium per day, which should usually stay at or below 400 mg from supplements.

## References

1. [Walker AF et al. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research, 2003.](https://pubmed.ncbi.nlm.nih.gov/14596323/)
2. [Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research, 2001.](https://pubmed.ncbi.nlm.nih.gov/11794633/)
3. [Schuette SA et al. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. Journal of Parenteral and Enteral Nutrition, 1994.](https://pubmed.ncbi.nlm.nih.gov/7815675/)
4. [Gröber U et al. Myth or reality: transdermal magnesium? Nutrients, 2017.](https://pubmed.ncbi.nlm.nih.gov/28788060/)
5. [National Institutes of Health Office of Dietary Supplements. Magnesium: fact sheet for health professionals.](https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/)