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.
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The short answer
There is no good evidence that magnesium causes depression. The research so far has looked at the opposite question, whether magnesium might help low mood. But some people do say they feel flat, tired or low after starting it, most often on higher doses or on magnesium glycinate. If that sounds familiar, a few simple changes are worth trying. And if low mood lasts more than two weeks, it deserves a proper conversation with your GP whatever you think the cause is.
What the research says
In a 2017 trial, 126 adults with mild to moderate depression took 248 mg of magnesium a day for six weeks. Their depression scores improved compared with the weeks they took nothing. The trial had no placebo group, so the result needs confirming, but it shows the direction researchers are looking in.
Depression is not listed as a side effect of magnesium by the NHS or the NIH. Lethargy can be a sign of too much magnesium in the body, but that is rare and mainly affects people with kidney problems or those taking very large doses.
Why you might feel low after starting magnesium
Feeling sedated can feel like feeling low
Magnesium is taken for its calming effect. For some people, particularly with glycinate, that tips over into feeling slowed down, unmotivated or emotionally flat. This is tiredness more than depression, but from the inside the two can be hard to tell apart.
The dose is higher than you need
The NHS says adults need about 270 mg (women) to 300 mg (men) of magnesium a day from all sources, and that 400 mg or less a day from supplements is unlikely to cause harm. Many people take more than this across several products without realising.
The low mood was already there
People often start magnesium because they are stressed, sleeping badly or already feeling low. If the supplement doesn’t help, the mood that was developing anyway can look like a side effect.
Other things in your routine
Poor sleep, alcohol, a recent illness, and some medicines can all lower mood. So can stopping a supplement or medicine you were taking before.
What to try
- Stop for one to two weeks and see whether your mood lifts. Magnesium supplements are safe to stop.
- If you restart, halve the dose and take it in the evening.
- Try a different form. If you take glycinate, citrate or malate may feel less sedating.
- Check the label for other ingredients, especially in sleep or relaxation blends.
- Keep a short diary of dose, sleep and mood. It makes patterns easier to see, and it is useful to show a GP.
An earlier version of this article suggested adding calcium and high-dose vitamin D to correct the problem. We have removed that advice because it isn’t supported by evidence. High-dose vitamin D carries risks of its own, which we explain in vitamin D and calcium: why more is not better.
When to see your GP
The NHS advises seeing a GP if you think you may be depressed. Book an appointment if:
- you have felt low, hopeless or lost interest in things for most of the past two weeks
- your mood is affecting work, relationships or sleep
- stopping magnesium made no difference
Don’t stop or change any prescribed medicine, including antidepressants, without speaking to your doctor. Tell them about any supplements you take.
See how magnesium interacts with other nutrients
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, read our magnesium side effects guide.
Sources
- Tarleton EK, et al. Role of magnesium supplementation in the treatment of depression: a randomized clinical trial. PLoS One, 2017.
- NHS. Vitamins and minerals: Others (magnesium).
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.
- NHS. Depression in adults.