In 30 seconds
- Magnesium is involved in more than 300 enzyme systems. An adult's body stores about 25 g, 50-60% of it in the bones.
- The EU recognises several authorised health claims for it, on the nervous system, the muscles or the bones. If you train, this is the one for you: “Magnesium contributes to normal muscle function”.
- EFSA sets an adequate intake of 350 mg a day for men and 300 mg for women. In the United States, 48% of the population does not get what it needs from its diet.
- For magnesium from supplements, the limit used in Europe is 250 mg a day for adults.
Whether you train or simply look after yourself, magnesium matters for three everyday things: tiredness, muscles and rest. Its authorised EU health claims include this one: “Magnesium contributes to a reduction of tiredness and fatigue”. And it makes most sense when your diet does not provide what you need, which is more common than it seems from a certain age onwards. A varied and balanced diet and a healthy lifestyle are important.
In your body
Where your magnesium is and how much it is involved in
What magnesium does in your body
An adult's body stores about 25 g of magnesium. Between 50 and 60% is in the bones and almost all the rest in soft tissues, such as muscle. Less than 1% is in the blood 1.
It is a helper for more than 300 enzyme systems 1. These are the main ones:
- Energy: it is needed to produce energy from what you eat.
- Muscles and nerves: it helps move calcium and potassium across cell membranes. That step is key for nerve impulses, muscle contraction and a normal heart rhythm.
- Proteins and DNA: it is involved in making proteins, DNA and glutathione, one of the body's own antioxidants.
- Bones: it is part of their structure.
What the European Union recognises
There are several authorised claims for magnesium, with official wording that cannot be changed. They apply to foods that are at least a source of magnesium 2:
| What for | Official wording |
|---|---|
| Tiredness | “Magnesium contributes to a reduction of tiredness and fatigue” |
| Nervous system | “Magnesium contributes to normal functioning of the nervous system” |
| Muscles | “Magnesium contributes to normal muscle function” |
| Energy | “Magnesium contributes to normal energy-yielding metabolism” |
| Mind | “Magnesium contributes to normal psychological function” |
| The body's minerals | “Magnesium contributes to electrolyte balance” |
| Proteins | “Magnesium contributes to normal protein synthesis” |
| Bones | “Magnesium contributes to the maintenance of normal bones” |
| Teeth | “Magnesium contributes to the maintenance of normal teeth” |
Source: Regulation (EU) No 432/2012, for foods that are at least a source of magnesium.
What it is good for: when it makes most sense
If you end the day tired
Magnesium contributes to a reduction of tiredness and fatigue 2. If you eat few nuts, pulses or wholegrains, it is easy to fall below the recommended amount.
If you want to rest better
This is where there are recent trials. In one from 2025, 155 adults aged 18 to 65 who slept poorly took bisglycinate providing 250 mg of magnesium, or placebo, each night, between 30 and 60 minutes before bed 5.
Over 4 weeks, their sleep scale improved by 3.9 points with magnesium and 2.3 with placebo. In an exploratory analysis, those who improved most were the people who ate the least magnesium 5. We tell you about it in detail in magnesium for sleep.
If you look after your bones
Magnesium contributes to the maintenance of normal bones 2. In population studies, a higher magnesium intake is associated with higher bone mineral density 1.
If you want to see all the studies on this mineral, from sleep to muscle, you will find them in magnesium: what the studies say.
How much you need and where to find it
EFSA sets an adequate intake of 350 mg a day for men and 300 mg for women. During pregnancy and breastfeeding, the reference is the same as for other women 3.
| Food | Portion | Magnesium |
|---|---|---|
| Roasted pumpkin seeds | 28 g | 156 mg |
| Roasted almonds | 28 g | 80 mg |
| Cooked spinach | Half a cup | 78 mg |
| Cooked black beans | Half a cup | 60 mg |
| Plain low-fat yoghurt | 227 g | 42 mg |
| Banana | 1 medium | 32 mg |
| Milk | 1 cup | 27 mg |
Source: NIH, Office of Dietary Supplements. Portions converted from ounces to grams (1 ounce = 28 g).
Of what you eat, your gut normally absorbs 30-40% 1. Nuts, seeds, cocoa, pulses, wholegrains and vegetables are the richest sources 4.
Who falls short
In the United States, 48% of the population gets less magnesium from food than it needs. Men over 70 and teenagers are the most likely to fall short 1.
These groups are at higher risk 1:
- Older people, for the reasons you will see in the next section.
- People with digestive problems such as Crohn's disease or coeliac disease, because of chronic diarrhoea and poor absorption.
- People with type 2 diabetes, because they lose more magnesium in their urine.
- People who drink too much alcohol, because they eat less magnesium and excrete more.
The first signs of a shortfall are not very specific: loss of appetite, nausea, tiredness and weakness 1. If you think you are short of it, check with your doctor. We explain more in magnesium deficiency.
Magnesium after 50
With age, three things come together: people tend to eat less magnesium, the gut absorbs less and the kidneys excrete more. It is also more common to take medicines that change its level, such as some diuretics or stomach protectors taken for more than a year 1.
The EFSA reference is the same at any adult age: 350 mg for men and 300 mg for women 3. If you are a woman going through the menopause, you may find magnesium during the menopause useful.
Bisglycinate: how it differs from other forms
Bisglycinate is magnesium bound to two molecules of glycine, in chelated form. It does the same as any magnesium. What changes is how much is absorbed and how well you tolerate it.
- Absorption: organic magnesium salts are absorbed better than inorganic ones. In a study in people, oxide barely raised blood magnesium: by 4.6%, the same as placebo 6.
- Compared with oxide: in 12 patients who were missing part of their intestine, diglycinate, another name for bisglycinate, was absorbed much better than oxide in those who absorbed oxide least well. And it was better tolerated 7.
- Tolerance: in the 2025 sleep trial, 93% of those who took it noticed no side effects at all 5.
Compared with citrate, another well-absorbed form, there are still few studies comparing the two directly 6. So rather than looking for a winning form, it makes sense to choose according to what you are looking for. We explain how in types of magnesium. At NG Advanced, our other supplement range, we explain what bisglycinate is and how to take it.
And in women
It does the same as in men. The EFSA reference for adult women is 300 mg a day, also during pregnancy and breastfeeding 3. If you are pregnant or breastfeeding, check with your doctor before taking a supplement.
Before you take it
Four things worth checking
Contraindications and safety
- Limit: the one used in Europe is 250 mg a day of magnesium from supplements for adults, not counting what comes from food. It is set to avoid mild diarrhoea 4.
- Side effects: with high doses, the most common are diarrhoea, nausea and stomach cramps 1.
- Medication: keep it at least 2 hours apart from bisphosphonates. With antibiotics such as tetracyclines or quinolones, take the antibiotic 2 hours before or 4-6 hours after the magnesium 1. The levothyroxine prescribing information says to take it at least 4 hours apart from antacids and calcium or iron supplements 8. Ask your doctor or pharmacist how to do this with magnesium.
- Kidneys, pregnancy and breastfeeding: if you have kidney disease, or are pregnant or breastfeeding, check with your doctor. When the kidneys are not working well, the risk of magnesium building up rises 1.
- Sleep Recovery: already contains magnesium. If you want to take both, check with your pharmacist or doctor first so you can adjust the total.
Frequently asked questions
What does magnesium do?
It is involved in more than 300 enzyme systems, from energy to muscle contraction. It has several authorised EU health claims, such as this one: “Magnesium contributes to a reduction of tiredness and fatigue”. Others concern the nervous system, the muscles and the bones.
What is taking magnesium good for?
Above all, for making sure you do not fall short if your diet does not reach 300-350 mg a day. In addition, in a 2025 trial with adults who slept poorly, magnesium bisglycinate improved their sleep more than placebo.
Is it good to take magnesium after 50?
With age, people tend to eat less magnesium, the gut absorbs less and the kidneys excrete more. So it is worth keeping an eye on it, starting with your diet. If you take medication, check with your doctor before adding a supplement.
What are the contraindications of magnesium bisglycinate?
If you have kidney disease, or are pregnant or breastfeeding, check with your doctor. Keep it apart from certain antibiotics, levothyroxine and bisphosphonates, and do not go over 250 mg a day of magnesium from supplements.
Can you take magnesium every day?
Yes, at the dose on the label. Studies have given it daily for weeks, and the European limit for magnesium from supplements is 250 mg a day for adults.
Sources
- Office of Dietary Supplements, National Institutes of Health. Magnesium: fact sheet for health professionals. View publication
- Commission Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children's development and health. View publication
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific opinion on dietary reference values for magnesium. EFSA Journal. 2015;13(7):4186. View publication
- Nordic Council of Ministers. Nordic Nutrition Recommendations 2023: magnesium. Nord 2023:003. View publication
- Schuster J, Cycelskij I, Lopresti A, Hahn A. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nat Sci Sleep. 2025;17:2027-2040. View publication
- Blancquaert L, Vervaet C, Derave W. Predicting and testing bioavailability of magnesium supplements. Nutrients. 2019;11(7):1663. View publication
- Schuette SA, Lashner BA, Janghorbani M. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN J Parenter Enteral Nutr. 1994;18(5):430-435. View publication
- AbbVie Inc. SYNTHROID (levothyroxine sodium) tablets: prescribing information. DailyMed, U.S. National Library of Medicine. Revised February 2024. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
