Dosing Magnesium Correctly in Sport: Requirements, Upper Limit, Cramps – and Which Product Fits

Calf cramp in extra time? Magnesium. Restless night? Magnesium. Hardly any mineral is recommended so reflexively – and hardly any is taken so often without looking at the dose. Yet magnesium is a good example of how much you can gain from reading the label carefully: in effect, in tolerance and in money.

In this article I explain how much magnesium you actually need, how to read the dose on the label correctly, when it becomes too much and what research says about cramps and sleep. At the end I compare the four magnesium products in our range. Which compounds exist and how they differ is described in detail by Selina Karl in Magnesium compounds compared – here the focus is on dosage.

What the body needs magnesium for

Magnesium is involved in more than 300 enzymatic reactions. For athletes, the following functions – for which the EU has authorised health claims – are particularly relevant:

Around 60 percent of the body's magnesium is stored in the skeleton, most of the rest in muscles and organs. Only about one percent is in the blood. That's why a normal blood value says little about the stores – and a low blood value is usually already a clear signal.

How much do you really need?

The German Nutrition Society gives an estimated value for adults of 300 mg a day for women and 350 mg for men. The EU nutrient reference value (NRV) on labels is 375 mg. There is no officially higher value for athletes. Minerals are lost through sweat, but only small amounts of magnesium – far less than sodium. And people who train a lot usually eat more and therefore automatically take in more magnesium.

Magnesium from food

With a varied diet, getting enough from food is quite achievable:

• Pumpkin seeds, 30 g150–170 mg
• Spinach cooked, 150 g80–90 mg
• Oats, 60 g80 mg
• Cashews, 30 g80 mg
• Almonds, 30 g75–80 mg
• White beans, 150 g70–80 mg
• Wholegrain bread, 2 slices50–80 mg
• Dark chocolate, 20 g40–45 mg

›Show data as table

Category	Magnesium per serving
Pumpkin seeds, 30 g	150–170 mg
Spinach cooked, 150 g	80–90 mg
Oats, 60 g	80 mg
Cashews, 30 g	80 mg
Almonds, 30 g	75–80 mg
White beans, 150 g	70–80 mg
Wholegrain bread, 2 slices	50–80 mg
Dark chocolate, 20 g	40–45 mg

A day with oats for breakfast, wholegrain bread, a handful of seeds and a serving of pulses or green vegetables usually reaches 350 mg and more. On the other hand, if you eat a lot of white flour, ready meals and few vegetables, you quickly fall short.

When a supplement can make sense

• Your diet contains few wholegrains, nuts, seeds, pulses and green vegetables.
• You are on a calorie-reduced diet and eat less overall.
• You train for long periods and sweat a lot, for example in endurance sessions in the heat or on tournament days.
• A doctor has found a low value or recommends magnesium, for example with certain medicines that flush out magnesium.

If, on the other hand, you eat well and have no symptoms, you don't need a magnesium supplement.

Elemental magnesium: the number that counts

Magnesium is always present in supplements as a compound – as citrate, bisglycinate, malate, taurate, gluconate or oxide. These compounds contain different amounts of the actual mineral:

The values vary with water content and manufacturing process. For you as a buyer this means: never calculate with the weight of the compound. What matters is the "magnesium" value in the nutrition table with its NRV percentage. Reputable labels also break down how much magnesium comes from which compound – our 4-fold Complex does so down to the milligram, for example.

How much is too much?

Germany's Federal Institute for Risk Assessment recommends no more than 250 mg of magnesium a day for food supplements, split into at least two servings. The European Food Safety Authority sets the same value as the tolerable upper limit for additional magnesium from supplements. The reason: above it, the risk of diarrhoea and gastrointestinal complaints increases, because unabsorbed magnesium draws water into the gut.

This limit doesn't apply to magnesium from food – pumpkin seeds don't cause diarrhoea. It matters for the total of all supplements: if you take a magnesium supplement plus an electrolyte drink or a multivitamin with magnesium, add them up.

Caution is needed with impaired kidney function, because excess magnesium is excreted via the kidneys. Magnesium can also reduce the absorption of certain antibiotics (tetracyclines, fluoroquinolones), osteoporosis drugs (bisphosphonates), iron and zinc. Two to three hours apart is a good rule of thumb; check with your doctor beforehand if you take medication.

Does magnesium help with cramps?

This is the most common question – and the answer is more sober than the advertising. Cramps during exercise, for instance in the calf in the third set or in the last kilometres of a run, are now thought to be caused mainly by fatigue of neuromuscular control: the muscle receives too many excitatory and too few inhibitory signals. Fluid and electrolyte losses can play a role but are rarely the sole cause.

A Cochrane review found no clinically relevant benefit of magnesium over placebo for typical muscle cramps in older people. There are hardly any good studies in athletes. The German consumer advice centre also points out that no effect against cramps should be expected without a deficiency.

What is more likely to help against exercise cramps:

• Adjust the load: cramps tend to occur when intensity is above your trained level.
• Train the muscles affected, especially strength and endurance of the calves and thighs.
• Stretch during an acute cramp – this usually breaks the reflex loop quickly.
• Drink enough and replace sodium in long sessions. What that looks like depending on duration and heat is covered in Electrolytes in sport.

Magnesium can still make sense if your intake really is low. It just isn't a cramp remedy.

Does magnesium help you sleep?

Here, too, the advertising is louder than the data. There are a few smaller studies, mainly in older people with low magnesium intake, showing slight improvements in sleep quality. For well-supplied, healthy athletes no effect has been demonstrated. The EU has not authorised any health claim about magnesium and sleep.

Many people still take magnesium in the evening because they tolerate it better with a meal. That's fine – just don't expect a sleep effect. What has been shown to help is covered in Sleep hygiene.

The Syrax magnesium products compared

We stock four magnesium products. They differ less in the "quality" of the compounds than in the dose, the form and the additives. All values come from the labels; prices are shop prices as of October 2026.

All four reports test heavy metals and microbiology – each without objection. An analysis of the actual magnesium content is not part of these standard tests.

• 4-fold Complex (tablet)€0.14
• Magnesium Shots€0.15
• 5x Complex + B6 (capsules)€0.17
• Mg + Zinc + B6 Gummies€0.33

›Show data as table

Category	Price per 100 mg of magnesium
4-fold Complex (tablet)	€0.14
Magnesium Shots	€0.15
5x Complex + B6 (capsules)	€0.17
Mg + Zinc + B6 Gummies	€0.33

My assessment

Magnesium 4-fold Complex – the standard. 200 mg mainly from well-tolerated bisglycinate, clearly declared, below the BfR recommendation and the cheapest product per milligram. For most athletes who want to supplement their diet, this is the first choice.

Magnesium 5x Complex + B6 – for split dosing. Two capsules with 250 mg in total – ideal for taking one capsule in the morning and one in the evening, as the BfR recommends. The vitamin B6 it contains (1.4 mg) corresponds to the daily requirement. To be honest: in 2024 the BfR lowered its proposal for B6 in supplements to 0.9 mg. The EFSA upper limit for total intake is considerably higher at 12 mg, so 1.4 mg is unproblematic for healthy adults – but if you also take a multivitamin with B6, add them up.

Magnesium Shots – the evening ritual with extras. Liquid, pleasant to take and combined with amino acids and vitamins. However, the 400 mg of magnesium per 15 ml is above the BfR recommendation, and 15 µg of vitamin D3 comes on top. My advice: if you take the shot long term, you can halve the serving or split it between two times of day – and you shouldn't take any other magnesium or vitamin D supplement in parallel. Because of the L-tryptophan, people taking antidepressants should seek medical advice first.

Magnesium + Zinc + B6 Gummies – for taste and routine. 200 mg of magnesium plus 10 mg of zinc. The most expensive per milligram of magnesium, but no swallowing and people like taking them. The zinc content is above the BfR proposal of 6.5 mg – not a problem for time-limited use, but a reason not to take zinc tablets at the same time. Sugar alcohols have a laxative effect in larger amounts; at the recommended two gummies, most people tolerate them well.

Who takes what? A decision guide

Intake: how magnesium is well tolerated

• Take it with a meal. That improves tolerance.
• Split larger amounts. Two smaller servings are gentler on the stomach than one large one and in line with the BfR recommendation.
• Keep a gap to iron, zinc and medication. Two to three hours.
• Don't double up to stock up. Magnesium isn't "stored" if you take extra once – the excess ends up in the gut.
• Soft stools are a signal. Then the single dose is too high or the compound doesn't suit you.

Conclusion: magnesium is a basic, not a miracle cure

Magnesium is an unspectacular but important building block. If you cover it well through your diet, you don't need a supplement. If you have gaps, a moderate dose of around 200 mg a day from well-tolerated compounds serves you well – ideally with a meal and split for larger amounts. Anything beyond that is no improvement for most people, just a risk for the stomach. And if you want to get rid of cramps, look at training load and sodium first, not in the magnesium tub.

How to assess supplements in general – from the label to the lab report – is explained in How to assess supplements. What is lost in sweat during long sessions is described by Werner in Electrolytes in sport.

Sources: DGE: FAQ magnesium – estimated intake values (German) · Verbraucherzentrale: Magnesium – what to consider (German) · Verbraucherzentrale: BfR maximum level proposals (statement 006/2024, German) · Cochrane Review: Magnesium for muscle cramps (Garrison et al., 2020) · EU Register of nutrition and health claims · Labels and lab reports of the Syrax products (as of October 2026)