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
Feeling jittery, shaky or wired isn’t a recognised side effect of magnesium. Magnesium is better known for the opposite, and very high levels in the body cause weakness and drowsiness, not jitters. So when people feel jittery after taking it, the cause is often something else in the product, something else in their day, or a dose that is upsetting their stomach.
This article is a checklist for working out which. If you feel worried or panicky more than physically shaky, our article on magnesium and anxiety is a better fit.
Get urgent medical help if you have chest pain, a heartbeat that won’t settle, fainting or difficulty breathing.
What jittery usually means
People use the word for a few different things: trembling hands, an inner buzzing or restlessness, a fast heartbeat, or feeling too alert to sit still. These are the same sensations caused by caffeine, too little sleep, low blood sugar and stress. The NHS lists caffeine, alcohol, nicotine, lack of sleep, stress and some medicines as common causes of palpitations.
That overlap is why it helps to rule out the everyday causes before blaming magnesium.
A checklist to work through
1. Read the full ingredients list
Many magnesium products are blends. Look for:
- Caffeine, guarana or green tea extract, common in energy and pre-workout formulas.
- B vitamins. Some people report feeling wired on high-dose B complex products.
- Other stimulating herbs such as ginseng.
- Sweeteners and flavourings in powders and gummies.
If your product is a blend, try a single-ingredient magnesium for comparison.
2. Check when you take it
If you take magnesium with your morning coffee or on an empty stomach, the jitters may be the coffee or the missed breakfast. Take it with a meal for a week and see whether anything changes.
3. Check the dose
The NHS says adults need about 270 mg (women) to 300 mg (men) of magnesium a day from all sources, and that more than 400 mg a day from supplements can cause diarrhoea. Stomach cramps, nausea and loose stools can leave you feeling shaky and unsettled. Add up everything you take, including multivitamins and electrolyte drinks, then try a lower dose.
4. Consider the form
Some readers say malate or L-threonate feels stimulating, and that glycinate feels calming. This is personal experience, not trial evidence, but it costs little to test. Change one thing and give it a week.
5. Look at the rest of your day
How much caffeine are you having? How are you sleeping? Have you started or stopped another supplement or medicine recently? Any of these can produce jitters that happen to coincide with a new magnesium habit.
6. Stop and restart
The clearest test is to stop magnesium for a week. If the jitters go, restart at half the dose. If they come back each time you take it, that product doesn’t suit you. If nothing changes when you stop, look elsewhere.
What not to do
You may read advice to take extra salt, potassium or calcium to balance magnesium. There is no good evidence that this fixes jitters, and potassium supplements in particular can be dangerous for people with kidney problems or on some blood pressure medicines. If you think an electrolyte is low, a blood test through your GP is the reliable way to find out.
When to speak to your GP
- A tremor or twitch that lasts more than two weeks.
- Palpitations that keep coming back or last longer than a few minutes.
- Jitters along with weight loss, sweating or feeling hot, which can point to a thyroid problem.
- You think a prescribed medicine is responsible. Don’t stop it without advice.
See how magnesium interacts with other nutrients
If you take several supplements, it helps to see how they relate. Tap magnesium on our free Mineral Interaction Wheel to see which minerals and vitamins it works with and which it may compete with. For the full list of magnesium side effects and fixes, read our magnesium side effects guide.
Sources
- NHS. Vitamins and minerals: Others (magnesium).
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.
- NHS. Heart palpitations.
- NHS. Twitching eyes and muscles.