Magnesium on Mounjaro, Wegovy & co.: which form, how much, what to watch for?

GLP-1 medications such as Mounjaro or Wegovy slow down digestion, and many users get constipated. At the same time you eat much less, so you also take in fewer minerals from food. The DGE (German Nutrition Society) recommends 350 mg of magnesium per day for men and 300 mg for women aged 25 and over – in total, from food and drink. Good sources are wholegrains, pulses, nuts, seeds and mineral water.

Under EU law, only authorised effects may be attributed to magnesium. These include that it contributes to normal muscle function, normal functioning of the nervous system, normal energy-yielding metabolism, electrolyte balance and the reduction of tiredness and fatigue. Nothing more is legally established, and we don’t promise anything more here either.

According to the German consumer advice centre (Verbraucherzentrale), organic compounds such as citrate are somewhat more soluble. But the difference hardly matters, and special effects of individual forms on specific organs (such as “glycinate for sleep”) are not proven.

Constipation: the laxative effect of magnesium salts is well known. They draw water into the gut. But: the amounts often needed for this are partly above the upper limit for food supplements. So if you want to use magnesium specifically as a laxative, discuss it with your doctor or pharmacy. The basics such as drinking, fibre and exercise are covered in Mounjaro and constipation.

Calf cramps: according to a Cochrane review, magnesium is unlikely to help older people with ordinary night-time cramps (moderate certainty). More common causes are too little fluid, overexertion or lack of exercise. On GLP-1 medications it is worth checking how much you drink (see drinking on a weight-loss injection).

Sleep: a meta-analysis of just three small studies in older adults found that they fell asleep about 17 minutes faster on average. However, the authors rate the evidence as “low to very low”. So magnesium is not a sleeping aid.

The BfR recommends taking no more than 250 mg of magnesium per day from food supplements, split into at least two portions. EFSA gives the same upper limit (Tolerable Upper Intake Level) for readily soluble magnesium salts and magnesium oxide from food supplements. Magnesium from normal food does not count towards it. The limit is based on the most common problem: diarrhoea.

According to the Verbraucherzentrale, 57 % of magnesium-containing products in one survey were above this recommendation. So look for the figure for elemental magnesium, not the weight of the compound. If your doctor recommends more, that is a medical decision for your individual case.

• Antibiotics (tetracyclines, quinolones such as ciprofloxacin): magnesium binds them in the gut. The NIH recommends taking the antibiotic at least 2 hours before or 4 to 6 hours after magnesium
• Osteoporosis medicines (bisphosphonate tablets): at least 2 hours apart
• Thyroid hormones, iron: here calcium and iron in particular are known to interfere. Ask your pharmacy whether you should keep a time gap
• Diuretics and acid blockers (PPIs): they can change your magnesium balance. That calls for medical monitoring, not self-dosing
• Blood pressure medicines such as ACE inhibitors or sartans: many electrolyte mixes contain potassium as well as magnesium. That can add up here, so check first

No direct interaction with magnesium is known for the weight-loss injection itself. More on combinations in weight-loss injection interactions.

• Cover your needs through diet first, then supplement specifically
• No more than 250 mg from supplements per day, split into two portions
• Take it with a large glass of water – that also helps against constipation
• Evening is practical if you take medicines in the morning that need a time gap
• If you get diarrhoea, reduce the amount or switch forms
• Add everything up: electrolyte sticks, multivitamins and magnesium capsules often each contain magnesium
• Look on the label for the amount of elemental magnesium per daily portion – not the weight of the compound
• Magnesium-rich mineral water is a simple alternative that also helps you drink enough

If you keep a diary of digestion, sleep and weight, you will see more quickly whether a change makes a difference – for example with the Tracker.

This is general information and not medical advice. Discuss magnesium with your doctor or pharmacy if you take medication.