This article is for general information only and is not medical advice. If you have a health condition, take prescribed medication or are pregnant, speak to your doctor or pharmacist before changing your supplements.
The short answer
Anxiety isn’t a recognised side effect of magnesium. The research that exists points the other way: magnesium is being studied as something that might ease mild anxiety. Even so, plenty of people say they feel more on edge after starting it. If that’s you, it is usually something you can sort out by changing the dose, the product or the timing.
Get urgent medical help if you have chest pain, a racing or irregular heartbeat that doesn’t settle, fainting or difficulty breathing. Those need checking whatever the cause.
What the research says
A 2017 systematic review of magnesium and anxiety found signs that it may help people who are prone to mild anxiety, but judged the quality of the evidence to be poor. Better trials are still needed.
None of those studies set out to look for anxiety as a side effect, and neither the NHS nor the NIH lists it as one. The well-established side effects are digestive: loose stools, nausea and stomach cramps, mostly at higher doses.
So there is no proven way in which magnesium causes anxiety. What follows are the most likely explanations, based on what is known about magnesium and on what readers tell us.
Why you might feel anxious after taking magnesium
Physical side effects that feel like anxiety
An upset stomach, nausea or a sudden need for the toilet can set off the same uneasy, on-edge feeling as anxiety. These effects depend on the dose. The NHS says more than 400 mg a day can cause diarrhoea, and some people react at lower doses, especially with citrate or oxide.
Something else in the product
Many magnesium products are blends. Check the label for added B vitamins, herbal extracts, sweeteners, or caffeine and green tea, which are common in energy formulas. If your symptoms started with a new product, magnesium may not be the ingredient responsible.
The form and the timing
People often find that one form suits them and another doesn’t, or that a morning dose feels different from the same dose at night. There are no good trials comparing forms for this, so it comes down to careful trial and error.
Something else changed at the same time
People usually start magnesium because they already feel stressed or are sleeping badly, and often change their diet or other supplements in the same week. Caffeine, alcohol, lack of sleep, stress and some medicines are all common causes of palpitations, according to the NHS. It’s worth looking at what else is different.
Watching for side effects
Starting any new supplement makes you pay closer attention to your body. Noticing a normal flutter or a restless night, and then worrying about it, can be enough to feed anxiety. The feeling is just as real, but the supplement may not be the cause.
What to try
Make one change at a time so you can tell what helped.
- Stop for a week. If the anxiety fades and then returns when you restart, that’s a useful clue. If nothing changes, magnesium probably isn’t the cause.
- Restart at a lower dose. Try half, taken with food.
- Add up your total. Count the magnesium in multivitamins, sleep blends, electrolyte drinks and sprays. The NHS says 400 mg or less a day from supplements is unlikely to cause harm.
- Switch to a single-ingredient product so you know exactly what you’re taking.
- Try a different form or time of day.
- Don’t add more supplements to fix it. Taking extra salt, potassium or calcium to balance magnesium isn’t supported by good evidence and can cause problems of its own. A varied diet covers these for most people.
When to speak to your GP
- Anxiety that lasts more than a couple of weeks or gets in the way of daily life, whether or not you take magnesium.
- Palpitations that keep coming back or last longer than a few minutes.
- You have kidney disease or a heart condition, or take regular medicine, and want to take magnesium.
Anxiety is common and treatable. The NHS has practical advice on anxiety, fear and panic, including how to refer yourself for talking therapies.
How magnesium fits with other nutrients
Magnesium doesn’t act alone. Tap magnesium on our free Mineral Interaction Wheel to see which minerals and vitamins it works with and which it may compete with. For other side effects, see our magnesium side effects guide, or if you feel physically wired rather than worried, read magnesium makes me jittery.
Sources
- NHS. Vitamins and minerals: Others (magnesium).
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.
- Boyle NB, Lawton C, Dye L. The Effects of Magnesium Supplementation on Subjective Anxiety and Stress: A Systematic Review. Nutrients, 2017.
- NHS. Heart palpitations.