Magnesium supplements: which form, how much per day and what to know

Short answer: A magnesium supplement contains magnesium bound to another substance, such as citrate, malate, bisglycinate or oxide. According to the Health Council of the Netherlands, adults need 300 mg (women) to 350 mg (men) of magnesium a day, and most of that comes from ordinary food. For magnesium from supplements there is an upper limit of 250 mg a day, so check the label for the amount of elemental magnesium, not just the weight of the salt.

Last updated: 5 November 2026 · Written by Florian Fermin

Magnesium supplements come in dozens of forms: capsules, tablets, powder, effervescent tablets and even oil for your skin. On the label you see names like citrate, bisglycinate or oxide, and often a number in milligrams that does not tell you how much magnesium you actually get. In this article you will read what those forms mean, how much magnesium per day is enough, what research says about absorption and sleep, and who should not simply take magnesium. We sell a magnesium complex with three forms ourselves. We mention it where it fits, but this article is about magnesium in general.

What is magnesium?

Magnesium is a mineral found in many everyday foods. According to the Dutch Nutrition Centre (Voedingscentrum), the main sources are wholemeal bread and other wholegrain products, vegetables, nuts, milk and dairy, and meat, and drinking water contributes too. A handful of unsalted nuts (25 grams) provides about 54 mg, a tablespoon of cooked spinach about 39 mg and a slice of wholemeal bread about 19 mg (Voedingscentrum).

According to the Voedingscentrum, a deficiency is uncommon because magnesium is found in so many foods. It can occur if your kidneys or intestines do not work properly. A blood test says little: only about 1% of the magnesium in your body is in your blood. If you are unsure whether you get enough, discuss it with your GP rather than guessing.

There are approved health claims for magnesium in the EU. A product may only use them if it provides enough magnesium per daily dose and this is properly substantiated on the label. For our Magnesium complex we currently make no health claims, so we do not make any in this article either.

What forms of magnesium are there?

In a supplement, magnesium is always bound to another substance. That substance determines the name and what percentage of the powder is actually magnesium. All forms in the table are on the European list of substances permitted in food supplements (Directive 2002/46/EC, Annex II). Magnesium L-threonate is an authorised novel food.

We calculated the percentages from the molecular formula of the anhydrous form. In practice they are often slightly lower, because raw materials contain water of crystallisation. The point is: 500 mg of magnesium bisglycinate is not 500 mg of magnesium, but about 70 mg. So always look for the line "of which elemental magnesium" or "magnesium" on the label.

Our Magnesium complex combines three forms. Each capsule contains 166 mg magnesium citrate, 168 mg magnesium malate and 166 mg magnesium bisglycinate, 500 mg of magnesium compounds in total, in a plant-based HPMC capsule.

Which magnesium is absorbed best?

That is less clear than many websites claim. Organic forms such as citrate did better than oxide in a few studies, but no clear winner has been shown between citrate, malate and bisglycinate. The dose and how much magnesium you already get probably matter more.

• In a randomised study, 46 healthy adults received 300 mg of magnesium a day for 60 days as citrate, as an amino acid chelate or as oxide, or a placebo. After 60 days the citrate and chelate groups excreted more magnesium in their urine than the oxide group, a sign that more had been absorbed. Oxide did not differ from placebo. It was a small study (Walker et al., 2003).
• In a laboratory test, magnesium citrate dissolved much better than magnesium oxide. After a single large dose, volunteers excreted more magnesium after citrate than after oxide (Lindberg et al., 1990).
• A 2017 review concludes that the type of magnesium salt matters less than is often thought. Some studies found slightly better absorption of organic salts, others did not. Small doses spread over the day are absorbed relatively better than one large dose (Schuchardt & Hahn, 2017).

I think that is honest information: anyone who says one form is "much better" is getting ahead of the research. We combine three common forms in one capsule, but we do not claim that this makes our Magnesium complex better absorbed than any other magnesium supplement.

How much magnesium per day?

According to the Health Council of the Netherlands, adult men need 350 mg of magnesium a day and adult women 300 mg. According to the Voedingscentrum and the European Food Safety Authority (EFSA), you should not take more than 250 mg of magnesium a day from a supplement. Magnesium from ordinary food does not count towards that.

The upper limit of 250 mg is based on bowel complaints such as diarrhoea. According to the Voedingscentrum, these can occur if you take in more than 250 mg a day extra, on top of your food (Voedingscentrum; EFSA, overview of upper levels 2025). If you use several products with magnesium, such as a multivitamin, an electrolyte powder or magnesium-rich mineral water, add everything up. In our article on electrolyte powder you can read how much magnesium it contains.

For our Magnesium complex, the directions say to take 1 to 2 capsules a day with water, preferably during or shortly after a meal. Do not exceed the recommended daily dose.

What does research say about magnesium and sleep?

The evidence is weak. There is no approved EU health claim about magnesium and sleep, so we do not say that magnesium helps you sleep better. There is research, though, and we describe it here as it is.

• A systematic review of 9 studies with a total of 7,582 adults found an association between magnesium status and sleep quality in observational research. The randomised studies contradicted each other. The authors call for larger and longer studies (Arab et al., 2023).
• A meta-analysis of 3 randomised studies in a total of 151 older adults with sleep problems looked at, among other things, the time it took to fall asleep and total sleep time. All studies had a moderate to high risk of bias and the quality of the evidence was low to very low. According to the authors, the research is too weak for well-founded advice (Mah & Pitre, 2021).

People also ask us whether magnesium taurate or magnesium bisglycinate is "better" for the night, or how magnesium compares with melatonin. We are not aware of studies that compare taurate and bisglycinate directly for sleep. Melatonin is something completely different: a hormone your body makes itself, not a mineral. If you have been sleeping badly for a long time, see your GP first.

Can you combine magnesium with calcium, vitamin B6 or L-theanine?

Yes, you see these combinations a lot, but keep an eye on the total amounts. Our Magnesium complex contains only the three forms of magnesium and the capsule: no calcium, no vitamin B6 and no other additives.

• Calcium and magnesium: many tablets contain both. A review names high doses of other minerals as one of the factors that can reduce magnesium absorption (Schuchardt & Hahn, 2017). If you want to take both, you can spread them over the day.
• Magnesium with vitamin B6: many people deliberately search for "magnesium without B6". Too much vitamin B6 over a longer period can cause symptoms. Add up the B6 from all your products, as we explain in our article on too much vitamin B6.
• Magnesium and L-theanine: two very different substances, a mineral and an amino acid from tea. What has been studied about L-theanine can be found in L-theanine: effects, dosage and use.
• Magnesium and ashwagandha: ashwagandha is a herb with its own warnings, including for pregnancy, thyroid and liver problems. Read those first before combining.

Who should be careful with magnesium?

The best-known side effect of too much magnesium from supplements is diarrhoea. Talk to your doctor or pharmacist first if your kidneys do not work as well as they should, if you are pregnant or breastfeeding, or if you take medication. The last three are also listed as warnings on our label.

• Kidneys: your kidneys regulate how much magnesium you lose. For magnesium as a medicine, Dutch pharmacists advise consulting your doctor if your kidneys work less well or if you are on dialysis (apotheek.nl).
• Medication: magnesium can reduce the absorption of some medicines. For magnesium hydroxide, for example, Dutch pharmacists advise taking certain antibiotics (such as doxycycline and ciprofloxacin), medicines for osteoporosis (such as alendronic acid) and thyroid hormone (levothyroxine) at least 2 hours earlier (apotheek.nl). If you use such medicines, ask your pharmacist whether this also applies to your supplement.
• Children: in France, supplements for children aged 4 to 10 and teenagers may provide at most 250 mg a day. According to the French government, supplements for babies and toddlers should only be used under the supervision of a healthcare professional (Compl'Alim). So do not simply give an adult supplement to a child.

What to look for when buying magnesium

First check how much elemental magnesium you get per daily dose, then the form and what else is in it. The form alone says little.

1. Elemental magnesium per daily dose. Stay below 250 mg a day from your supplement, unless your doctor advises otherwise.
2. The form. Citrate, malate and bisglycinate are common organic forms. Oxide provides a lot of magnesium per gram. Which form is absorbed best is not clear, as explained above.
3. Extra ingredients. Does it contain vitamin B6, calcium or zinc? Count them together with your other products.
4. Capsule, tablet or powder. Capsules and tablets are easy to dose. Powder can be split, but measure it carefully.
5. Vegan or not. An HPMC capsule is plant-based, a gelatine capsule is not.

Our Magnesium complex is vegan, contains three forms in one capsule and is independently tested for quality and purity. If you want to take a look, you can buy magnesium here. Our other minerals and vitamins can be found under vitamins and minerals.

Summary in 3 points

• Magnesium in supplements is bound to another substance. Look at the amount of elemental magnesium, not the weight of the salt.
• Adults need 300 to 350 mg a day, mainly from food. From supplements, no more than 250 mg a day.
• Organic forms did better than oxide in a few studies, but there is no clear best form. For magnesium and sleep the evidence is weak and there is no approved claim.

Frequently asked questions

When is the best time to take magnesium?

A fixed time is not necessary. Our directions say during or shortly after a meal. If you use medicines such as antibiotics or thyroid hormone, ask your pharmacist how much time you should leave in between.

What is the difference between magnesium glycinate and magnesium bisglycinate?

They usually mean the same thing: magnesium bound to two molecules of glycine. On the European list it is called magnesium bisglycinate.

Does your magnesium contain vitamin B6?

No. Our Magnesium complex contains only magnesium citrate, magnesium malate, magnesium bisglycinate and an HPMC capsule.

Is magnesium oil the same as a magnesium supplement?

No. Magnesium oil is a solution of magnesium chloride that you rub on your skin. This article is about magnesium you swallow. How much magnesium is absorbed through the skin has not been well studied.

Can I get too much magnesium?

Not easily from ordinary food. From supplements you can: above 250 mg a day extra, bowel complaints such as diarrhoea can occur. If your kidneys do not work well, caution is needed, so talk to your doctor first.

Sources

1. Voedingscentrum (Netherlands Nutrition Centre). Encyclopaedia: magnesium (adequate intake according to the Health Council, upper limit for supplements, food sources), accessed 5 November 2026. voedingscentrum.nl
2. EFSA. Overview on Tolerable Upper Intake Levels as derived by the SCF and the EFSA NDA Panel, version 11, August 2025 (magnesium from supplements: 250 mg per day). efsa.europa.eu (PDF)
3. EFSA NDA Panel. Scientific Opinion on Dietary Reference Values for magnesium. EFSA Journal. 2015;13(7):4186. doi:10.2903/j.efsa.2015.4186. doi.org
4. Directive 2002/46/EC on food supplements, Annex II (permitted magnesium forms), consolidated version. eur-lex.europa.eu
5. Regulation (EU) No 1169/2011, Annex XIII (reference intake magnesium 375 mg). eur-lex.europa.eu
6. Compl'Alim (French government), ingredient record magnesium bisglycinate: maximum 360 mg magnesium per day for adults, 250 mg for children aged 4 to 17, accessed 5 November 2026. compl-alim.beta.gouv.fr
7. Walker AF, Marakis G, Christie S, Byng M. Randomised, double-blind study in 46 healthy adults, 60 days of 300 mg magnesium per day as citrate, amino acid chelate or oxide. Magnes Res. 2003;16(3):183-191. PubMed 14596323
8. Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. Solubility (laboratory) and absorption (single dose in healthy volunteers) of magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990;9(1):48-55. doi:10.1080/07315724.1990.10720349. doi.org
9. Schuchardt JP, Hahn A. Review of magnesium absorption and factors influencing bioavailability. Curr Nutr Food Sci. 2017;13(4):260-278. doi:10.2174/1573401313666170427162740. doi.org
10. Arab A, Rafie N, Amani R, Shirani F. Systematic review of 9 observational and randomised studies (7,582 adults) on magnesium and sleep. Biol Trace Elem Res. 2023;201(1):121-128. doi:10.1007/s12011-022-03162-1. doi.org
11. Mah J, Pitre T. Systematic review and meta-analysis of 3 randomised studies (151 older adults with sleep problems) on magnesium. BMC Complement Med Ther. 2021;21(1):125. doi:10.1186/s12906-021-03297-z. doi.org
12. Apotheek.nl (Royal Dutch Pharmacists Association, KNMP). Magnesium hydroxide: use with other medicines and with reduced kidney function, accessed 5 November 2026. apotheek.nl
13. GOYU, label and product page Magnesium complex (composition per capsule, directions and warnings), accessed 5 November 2026.

This article is for information only and is not medical advice. Food supplements are not a substitute for a varied and balanced diet and a healthy lifestyle. If in doubt, pregnant, if you have kidney problems or take medication, talk to your GP or pharmacist.