How Long Does Magnesium Take to Work?

If you've just started taking magnesium, you're probably wondering when you'll notice a difference. Will it work today, or does it take weeks?

The short answer: your body starts absorbing magnesium within hours, but how long it takes to notice anything depends on why you're taking it. As a laxative, it can work within hours. For relaxation, some people notice a difference within a few days. For sleep, or to top up low levels, expect it to take several weeks of daily use.

How long does magnesium take to work?

This is a realistic timeline, depending on what you're taking it for.

These are typical timeframes, not guarantees. Everyone is different, and what you eat, which type you take and how low your levels were to start with all make a difference.

How long does magnesium take to work for sleep?

Magnesium isn't a sleeping pill, so it won't knock you out. Some people say they feel calmer within the first few nights, often helped by the routine of taking it. If it's going to make a difference, many people start to notice it after a week or two, and most research on magnesium and sleep has measured results over four to eight weeks.

The evidence is promising but limited. A 2021 review of studies in older adults found that magnesium may help people fall asleep a little faster, but the studies were small and the quality of evidence was low. It's most likely to help if your magnesium levels are low to begin with.

How long does magnesium glycinate take to work?

Magnesium glycinate is one of the most popular forms for sleep because it's well absorbed and gentle on the stomach. It's absorbed within hours, but like other forms, you should expect it to take a week or two of regular use before you notice a difference, and longer to see the full effect.

Magnesium citrate is also well absorbed, and works faster as a laxative. Magnesium oxide is less well absorbed, so it may take longer to top up your levels.

How long does magnesium take to work for muscle cramps?

Magnesium is often recommended for cramps, but the evidence isn't strong. A 2020 Cochrane review found that magnesium is unlikely to help typical muscle cramps in older adults. If you get cramps often, speak to your GP, as there can be other causes.

Why doesn't magnesium work straight away?

Magnesium is a mineral your body uses for hundreds of everyday processes, including how your nerves and muscles work. Most of it is stored in your bones and tissues, not your blood. If you've been running low, your body needs time to build those stores back up, which can take weeks of regular intake. That's why taking it consistently matters more than any single dose, and why taking more won't make it work faster.

What affects how quickly magnesium works?

• Your starting levels. People who are low in magnesium are the most likely to notice a difference.
• Consistency. Taking it every day, at a similar time, gives it the best chance.
• The type of magnesium. Forms such as glycinate and citrate are absorbed better than magnesium oxide.
• Your diet. Leafy greens, nuts, seeds, beans and wholemeal bread all provide magnesium.
• The rest of your routine. For sleep, late caffeine, alcohol and screens can easily cancel out any benefit.

Signs you might be low in magnesium

Low magnesium isn't easy to spot, and the signs overlap with lots of other things. They can include tiredness, muscle cramps or twitches, and feeling weak. If you're worried about your levels, speak to your GP, who can check them with a blood test.

Make magnesium part of your wind-down

Because magnesium works best when you take it consistently, it helps to tie it to something you already do every evening. Vidrate Night is a zero-sugar mixed berry drink with magnesium, L-theanine, zinc and lemon balm, and no caffeine. Magnesium contributes to the normal functioning of the nervous system and the reduction of tiredness and fatigue. Mix a sachet with 300ml of water, hot or cold, 30 to 40 minutes before bed. Vidrate Night isn't suitable for under 18s.

When and how much to take

For sleep, most people take magnesium in the evening, 30 to 60 minutes before bed. For general health, any time of day works, as long as it's consistent. The NHS says 400mg or less a day from supplements is unlikely to cause harm. For timing, food, splitting your dose and which type to choose, read our guide to the best time to take magnesium.

Speak to your GP or a pharmacist before taking magnesium if you have kidney disease, are pregnant or breastfeeding, or take other medicines.

Frequently asked questions

Does magnesium work straight away?

Your body starts absorbing magnesium within hours, but most effects, including on sleep, build up over days and weeks rather than hours. The exception is its laxative effect, which can work within a few hours.

How quickly does magnesium put you to sleep?

It doesn't. Magnesium won't make you fall asleep the way a sleeping pill does. It's best thought of as part of a good evening routine.

What happens when you start taking magnesium every day?

Most people notice very little at first. Over the following weeks, some find they feel calmer in the evening or fall asleep a little more easily. The most common side effect is an upset stomach or loose stools, especially at higher doses.

Will taking more magnesium make it work faster?

No. Your body can only absorb so much at once, and taking more than 400mg a day from supplements can cause diarrhoea. Regular, moderate amounts work better.

How long should I try magnesium before giving up?

Give it at least four to eight weeks of daily use. If you still don't notice any difference, it may not be what's affecting you, and it's worth speaking to your GP if problems continue.

The bottom line

Magnesium is absorbed within hours, but most of its effects take longer. Some people feel calmer within a few days, while sleep and low levels usually need four to eight weeks of daily use. Take it consistently, stay within 400mg a day from supplements, and speak to your GP if problems carry on.

Sources: NHS, Vitamins and minerals: magnesium. Mah J and Pitre T (2021), Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis, BMC Complementary Medicine and Therapies. Garrison SR et al. (2020), Magnesium for skeletal muscle cramps, Cochrane Database of Systematic Reviews.