When to take magnesium, and how long it takes to work
Morning or night, with or without food, how long it takes to work, and which medicines and supplements to keep apart from magnesium.
- Written by
- Amy D
- Reviewed by
- Nooroots team
- Last updated
- Reading time
- 8 min read
Overview
Take magnesium at the time you'll remember every day: no trial has compared morning with evening. For sleep, take it 30 to 60 minutes before bed. Leave 2 to 3 hours between magnesium and other medicines. In a 2025 sleep trial, most of the benefit came within 2 weeks; blood levels keep rising for months.
Key points
- Timing: no time of day has been shown to work better, so pick one you'll keep to.
- Sleep: take it 30 to 60 minutes before bed, as in a 2025 trial.
- Medicines: leave 2 to 3 hours between magnesium and other medicines.
- How long: sleep changes within 2 to 4 weeks; blood levels settle after about 20 weeks.
- Amount: the NHS says 400 mg a day or less from supplements is unlikely to cause harm.
The best time to take magnesium
When to take magnesium matters less than taking it every day. No trial has compared taking it in the morning with taking it at night, so the best time is the one you'll stick to.
Your goal can still steer the timing. If you take it for sleep, take it in the evening. If you take other medicines, leave a gap between them and your magnesium.
| Your goal | When to take it | Why |
|---|---|---|
| Better sleep | 30 to 60 minutes before bed | The timing used in a 2025 sleep trial [2] |
| Less tiredness, general top-up | Any time that suits you | No time of day has been shown to work better |
| A larger amount | Split across the day | Your body absorbs a smaller share of a big dose [7] |
| You take other medicines | 2 to 3 hours apart from them | Magnesium can stop some medicines being absorbed [7] |
Magnesium in the morning or at night?
Either is fine. No human study has tested whether one works better than the other, for sleep or anything else.
Night suits most people who take it for sleep. In a 2025 trial of 155 adults who slept poorly, people took 250 mg of magnesium as bisglycinate 30 to 60 minutes before bed. Their sleep scores improved a little more than on a placebo, and most of the change came in the first 2 weeks [2].
Morning suits you if that's when you remember. Just keep it apart from any medicines you take at breakfast.
Should you take magnesium with food?
You can take it with or without food. If magnesium upsets your stomach, try it with a meal.
The size of the dose matters more. Your gut absorbs a smaller share of magnesium as the amount rises [7], which is why UK magnesium medicines are taken in smaller doses through the day. If you take more than one capsule, spreading them out is a simple option.
When should you take magnesium glycinate?
In the evening if you take it for sleep, since the 2025 sleep trial gave bisglycinate before bed [2]. For anything else, any time of day works, morning included.
The same goes for other forms. Read more in our guides to magnesium glycinate, magnesium citrate and magnesium malate.
How long does magnesium take to work?
Give it 2 to 4 weeks for sleep, and longer for your levels to build. Magnesium isn't a quick fix: it tops up a mineral your body uses every day.
| Goal | What studies found | Evidence |
|---|---|---|
| Sleep | Most of the improvement came in the first 2 weeks, measured at 4 weeks [2] | Early |
| Magnesium in your blood | Rises steadily and levels off after about 20 weeks, across 48 trials [3] | Moderate |
| Night-time leg cramps | Unlikely to help older adults, even after 4 weeks [4] | Strong |
The blood-level research also found that people who started with lower levels gained the most [3]. So if your diet is low in magnesium, you're the most likely to notice a difference.
For more on sleep, see magnesium for sleep: what the research shows.
Which medicines should you space from magnesium?
Several, because magnesium can stop some medicines being absorbed properly. UK magnesium medicine leaflets advise leaving 2 to 3 hours between magnesium and other medicines where you can [7].
| Medicine | Gap to leave |
|---|---|
| Ciprofloxacin | Take it 1 to 2 hours before, or at least 4 hours after, magnesium [8] |
| Tetracycline antibiotics, such as doxycycline | 2 to 3 hours or more [7] |
| Bone medicines, such as alendronic acid | 3 to 4 hours [7] |
| Levothyroxine | Take it 30 to 60 minutes before breakfast and any other medicine [10] |
Two more groups can lower your magnesium over time. Water tablets, such as bendroflumethiazide and furosemide, increase the magnesium you lose in urine [7]. Heartburn tablets called PPIs, such as omeprazole and lansoprazole, can rarely cause low magnesium with long-term use, mostly after a year or more [9].
Magnesium and blood pressure tablets
Most people can take them together. The NHS pages for amlodipine, ramipril, losartan, bendroflumethiazide and indapamide don't list magnesium as an interaction [10].
Magnesium can lower blood pressure slightly on its own. Across 34 trials, about 370 mg a day lowered it by around 2 mmHg compared with a placebo [5]. That's small, but tell your GP or pharmacist when you start, and keep it 2 to 3 hours apart from your tablets [7].
Magnesium with zinc, iron or vitamin D
You can take them together, with one gap to remember. Many multivitamins contain both magnesium and zinc; the NHS advises keeping zinc supplements to 25 mg a day or less [1]. Leave 3 to 4 hours between magnesium and iron, as UK magnesium leaflets advise [7].
Vitamin D pairs well with magnesium. In a 12-week trial of 180 adults aged 40 to 85, magnesium raised vitamin D levels in people who started in the middle range. In people who started high, it brought levels down [6]. No study has tested what time of day to take the two.
How much magnesium a day?
The NHS says adults aged 19 to 64 need 270 mg (women) or 300 mg (men) a day, and that 400 mg or less a day from supplements is unlikely to cause harm [1]. Taking more than 400 mg for a short time can cause diarrhoea [1].
A varied diet can give you all you need [1]. Count the magnesium in every supplement you take, multivitamins included.
Where Nooroots fits
Nooroots Triple Magnesium gives you 301 mg of magnesium from glycinate, citrate and malate in three capsules a day. Take all three together in the evening as part of winding down, or spread them through the day.
Triple Magnesium's magnesium contributes to a reduction of tiredness and fatigue and to normal psychological function.
Coming soon. Triple Magnesium isn't on sale yet.
Frequently asked questions
How long before bed should I take magnesium?
About 30 to 60 minutes before bed. That's the timing used in a 2025 trial in which magnesium improved sleep scores a little more than a placebo [2].
Can I take magnesium glycinate in the morning?
Yes. Nothing suggests the time of day changes how well it works. Evening suits people taking it for sleep, but any time is fine otherwise.
Does magnesium work straight away?
No. Blood magnesium rises steadily over weeks and levels off after about 20 weeks [3]. In a sleep trial, most of the benefit came within 2 weeks [2].
How long does magnesium glycinate take to work for sleep?
In the 2025 trial, most of the improvement came in the first 2 weeks and lasted to the end at 4 weeks [2].
Can I take vitamin D and magnesium at night?
Yes. They can be taken together at any time of day, and no study has found a best time for either.
Can I take magnesium every day?
Yes, for most adults, as long as the magnesium from all your supplements stays at 400 mg a day or less [1].
Can you take ashwagandha and magnesium together?
Yes. No interaction is known. See our guide to taking ashwagandha and magnesium together.
References
Every study here is listed so you can read it yourself. This guide is for general information and doesn't replace advice from your GP or pharmacist. We review it when new research is published.
- NHS. Vitamins and minerals: others (magnesium and zinc sections). Accessed 17 October 2026. nhs.uk/conditions/vitamins-and-minerals/others
- Schuster J et al. (2025). Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nature and Science of Sleep 17: 2027–2040. doi:10.2147/NSS.S524348
- Zhang X et al. (2016). The circulating concentration and 24-h urine excretion of magnesium dose- and time-dependently respond to oral magnesium supplementation in a meta-analysis of randomized controlled trials. Journal of Nutrition 146(3): 595–602. PMID 26865651
- Garrison SR et al. (2020). Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews 9: CD009402. PMID 32956536
- Zhang X et al. (2016). Effects of magnesium supplementation on blood pressure: a meta-analysis of randomized double-blind placebo-controlled trials. Hypertension 68(2): 324–333. PMID 27402922
- Dai Q et al. (2018). Magnesium status and supplementation influence vitamin D status and metabolism: results from a randomized trial. American Journal of Clinical Nutrition 108(6): 1249–1258. PMID 30541089
- Neoceuticals Ltd. Neomag 4 mmol chewable tablets: Summary of Product Characteristics (sections 4.3, 4.5 and 5.2). Electronic medicines compendium, updated 28 September 2026. medicines.org.uk/emc/product/2678/smpc
- Ciprofloxacin 500 mg film-coated tablets: Summary of Product Characteristics (section 4.5). Electronic medicines compendium, updated 9 June 2026. medicines.org.uk/emc/product/7257/smpc
- Medicines and Healthcare products Regulatory Agency (2012). Proton pump inhibitors in long-term use: reports of hypomagnesaemia. Drug Safety Update 5(9): A1. gov.uk/drug-safety-update
- NHS. Medicines A to Z: levothyroxine, amlodipine, ramipril, losartan, bendroflumethiazide and indapamide. Accessed 17 October 2026. nhs.uk/medicines
