Last updated: 12 November 2026
Magnesium glycinate side effects are uncommon and usually mild: loose stools, nausea or stomach cramps, mostly when people take more than 400mg of magnesium a day from supplements. It tends to be gentler on the gut than oxide or citrate. People with kidney disease, and anyone on antibiotics, levothyroxine or bisphosphonates, should check with a pharmacist first.
Below: what side effects to expect and how common they are, why glycinate is easier on the stomach, safe daily amounts, who should avoid it, which medicines to space apart, and the rare signs of too much magnesium. This is general information, not medical advice.
What are the side effects of magnesium glycinate?
The side effects of magnesium glycinate are mainly digestive: loose stools, nausea, stomach cramps or wind. They are more likely at higher doses, on an empty stomach, or when a “glycinate” product also contains oxide or citrate. Serious problems such as dangerously high blood magnesium are rare and mostly affect people with kidney disease.
| Side effect | How likely | What usually helps |
|---|---|---|
| Loose stools or diarrhoea | The most common, mainly above 400mg a day | Lower the dose, split it, take it with food |
| Nausea or stomach cramps | Occasional, often on an empty stomach | Take it with a meal |
| Headache | Reported by some users; not linked to glycinate in trials | Check fluids, caffeine and other causes |
| Drowsiness | Not seen more than with a placebo in trials | Check what else is in the product |
| High blood magnesium | Rare; mostly kidney disease or very large doses | Medical help (see signs of too much magnesium) |
The best trial data come from a 2025 German study of 155 adults who took 250mg of magnesium a day as bisglycinate, or a placebo, for four weeks. Most people reported no side effects at all. Two side effects were reported in the magnesium group (one person with dizziness and nausea, one with joint pain) against seven in the placebo group, and nobody stopped taking magnesium because of side effects.
That is one short trial in healthy adults, so it doesn’t rule out problems at higher doses or over longer periods. For other forms of magnesium, sprays and complexes, see our full guide to magnesium side effects for every form.
Is magnesium glycinate gentler on the stomach?
Yes, magnesium glycinate is usually gentler on the stomach than magnesium oxide or citrate. It is magnesium bound to the amino acid glycine, so less loose magnesium sits in the bowel drawing in water. Oxide and citrate do this more, which is why they are used as laxatives. At very high doses, any form can still loosen stools.
The evidence for “gentler” is real but thin. A small 1994 trial in 12 people who had part of their bowel removed found magnesium glycinate was better tolerated than oxide by every patient, and was absorbed better by the four who absorbed oxide worst. In the 2025 trial above, stomach complaints were no more common with bisglycinate than with the placebo.
Two label points matter more than the name on the front:
- Blends: many products sold as “glycinate” also contain oxide or citrate, which add a laxative effect. Read the ingredients list. Our chart of magnesium types shows how each form behaves.
- Elemental magnesium: bisglycinate is only about 14% magnesium by weight, so 1,000mg of magnesium bisglycinate gives roughly 141mg of magnesium. Side effects follow the magnesium figure, not the compound weight.
If you want the laxative effect, for example for constipation, glycinate is the wrong choice: see magnesium for constipation and magnesium citrate instead. Glycinate and bisglycinate are the same thing under two names.
What to do if magnesium glycinate upsets your stomach
If magnesium glycinate gives you loose stools or nausea, the usual fix is a smaller dose taken with food. Most digestive side effects settle within a few days of cutting back. Diarrhoea that lasts more than 7 days, or signs of dehydration, need a call to NHS 111 or your GP.
- Halve the dose for a week, then build up again slowly.
- Take it with a meal rather than on an empty stomach.
- Split larger amounts into a morning and an evening dose.
- Add up every source: multivitamins, antacids, laxatives and “complex” products often contain magnesium too.
- Check the form: if your product contains oxide or citrate, a pure bisglycinate may suit you better.
Timing makes little difference to how well magnesium works, so choose whatever time suits your stomach. Our guide to the best time to take magnesium covers morning versus evening, and how long magnesium stays in your body explains why missing a day doesn’t matter.
Does magnesium glycinate cause drowsiness or headaches?
Magnesium glycinate is not a sedative, and trials have not found it causes drowsiness. In the 2025 trial, daytime sleepiness changed no more with bisglycinate than with the placebo, and the only headache reported was in the placebo group. Some people still report grogginess, headaches or vivid dreams, so a lower dose is sensible.
If you feel drowsy after starting a magnesium product, check the full ingredients: many blends add herbal extracts, which can affect people differently. Don’t drive if you feel drowsy for any reason. Our guide to whether magnesium makes you sleepy goes into the research, and the main magnesium glycinate guide covers what it is and how long it takes to notice anything.
Headaches and vivid dreams after magnesium are mostly reported anecdotally, without trial evidence either way. A headache that is new, severe or keeps coming back needs a GP, whatever you think the cause is.
How much magnesium glycinate is safe a day?
The NHS says adults need 300mg of magnesium a day (men) or 270mg (women), mostly from food, and that 400mg or less a day from supplements is unlikely to cause harm. More than 400mg in a short time can cause diarrhoea. These figures are elemental magnesium, not the weight of the glycinate compound.
| Guide figure | Magnesium a day | What it covers |
|---|---|---|
| NHS need: women | 270mg | Total from food and supplements |
| NHS need: men | 300mg | Total from food and supplements |
| NHS supplement guide | 400mg or less | Supplements only; unlikely to cause harm |
| EFSA upper level | 250mg | Supplements, fortified foods and water only |
| GB label NRV | 375mg | The 100% figure used on labels |
The European Food Safety Authority sets a more cautious upper level of 250mg a day from supplements, based on the dose at which mild diarrhoea starts to appear in some people. The NHS figure is the one usually used in the UK. Either way, food magnesium doesn’t count towards these limits, because healthy kidneys handle it easily.
For amounts by age and sex, see how much magnesium per day. Over 60 and taking several medicines? Read magnesium for older adults first.
Who should not take magnesium glycinate?
People with kidney disease should not take magnesium glycinate unless their kidney team or GP advises it, because weak kidneys can’t clear extra magnesium. Anyone with a very slow heartbeat or heart block, or with myasthenia gravis, should also ask a doctor first. Check with a pharmacist if you take regular medicines.
- Kidney disease: the biggest risk group for magnesium building up in the blood.
- Heart rhythm problems: such as heart block or a very slow heartbeat. Magnesium may also lower blood pressure slightly; our guide to magnesium and blood pressure explains what trials found.
- Myasthenia gravis: magnesium can make muscle weakness worse.
- Pregnancy and breastfeeding: talk to your midwife or GP first. See magnesium in pregnancy.
- Children: need much smaller amounts and a product made for their age.
Our products are for adults only, and we don’t recommend them during pregnancy or breastfeeding.
Magnesium glycinate and medicines: what to space apart
Magnesium glycinate can stop some medicines being absorbed properly if you take them at the same time. The main ones are some antibiotics (doxycycline, ciprofloxacin), levothyroxine and bisphosphonates such as alendronic acid. Taking them a few hours apart usually solves it, but ask your pharmacist for the gap that suits your medicine.
| Medicine | The problem | Gap often advised |
|---|---|---|
| Tetracycline and quinolone antibiotics (doxycycline, ciprofloxacin) | Magnesium binds them in the gut | Antibiotic at least 2 hours before, or 4 to 6 hours after, magnesium |
| Bisphosphonates (alendronic acid, risedronate) | Less of the medicine is absorbed | At least 2 hours apart; follow the leaflet’s empty-stomach rules |
| Levothyroxine | Minerals can reduce absorption | Often about 4 hours apart; ask your pharmacist |
| Long-term acid reducers (omeprazole, lansoprazole) | Can lower magnesium levels over time | Your GP may check your levels |
| Water tablets (diuretics) | Can raise or lower magnesium | Check with your GP |
The NHS levothyroxine page lists antacids and calcium and iron supplements among the things that may not mix well with it, and asks you to tell your doctor or pharmacist about any supplements. The antibiotic and bisphosphonate gaps above come from the US National Institutes of Health fact sheet on magnesium. Your medicine’s own leaflet always comes first.
Never stop or change a prescribed medicine to make room for a supplement. If you take several medicines, a pharmacist can plan the timings with you for free.
Signs of too much magnesium
Too much magnesium from supplements usually shows first as diarrhoea, which is the body’s way of getting rid of it. Dangerously high blood magnesium (hypermagnesaemia) is rare and mostly happens with kidney disease or very large doses of magnesium laxatives or antacids. Its signs include weakness, flushing, low blood pressure and a slow heartbeat.
- Early signs: nausea, vomiting, flushing of the face and feeling weak or lethargic.
- Later, serious signs: muscle weakness, very low blood pressure, a slow or irregular heartbeat and difficulty breathing.
iCall 999 for difficulty breathing, a very slow or irregular heartbeat, severe weakness or collapse. For milder symptoms that worry you, call NHS 111 or speak to your GP. Our main side effects guide has more on high magnesium symptoms and blood test ranges.
iLow magnesium can cause some similar-sounding symptoms, such as tiredness and muscle cramps. If you’re unsure which applies, see signs of magnesium deficiency and ask your GP about a blood test.
Where Evopure fits
Evopure makes one magnesium product. The Magnesium Glycinate Sleep Complex is a berry-flavoured drink powder with 290mg of magnesium (77% NRV) per 4.75g serving, from 1,000mg magnesium bisglycinate and 900mg magnesium citrate. It also contains 500mg glycine, 100mg L-theanine, oat straw, hops, chamomile and passionflower, which are listed as ingredients only. It is vegan and made in the UK.
Because it includes citrate, start with a smaller serving if your stomach is sensitive, and take it with food. At 290mg it sits inside the NHS 400mg guide for supplements, so check the labels of anything else you take that contains magnesium. Magnesium contributes to a reduction of tiredness and fatigue and to normal psychological function.
The Reishi Mushroom Adaptogenic Complex is a reishi hot chocolate with 0.5g reishi, 0.5g maca and 0.3g cinnamon per 8g, and contains a little natural caffeine from the cocoa. Its pack says it is not for pregnant or nursing women or people on medication. The Broad Spectrum CBD Capsules give one 10mg capsule of CBD, so there is nothing to measure. They are for adults only. If you take any regular medicines, check with a GP or pharmacist first.
The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.
Next step
Magnesium Glycinate Sleep Complex
If you want a magnesium top-up in a drink rather than another tablet, the Magnesium Glycinate Sleep Complex gives 290mg of magnesium (77% NRV) per 4.75g serving from bisglycinate and citrate. Magnesium contributes to a reduction of tiredness and fatigue.
Add Magnesium Glycinate Sleep Complex to bag See ingredients and reviews
Rated 4.7 out of 5 from 15 verified ratings on the product page (via Lipscore, checked 12 November 2026). Vegan and made in the UK. Subscribe and save 25% on your first order, then 20%. New to Evopure? Join our emails for 20% off a one-off first order. Free UK delivery over £40. Black Friday, 27 to 30 November: see our Black Friday magnesium and supplement deals. Have kidney disease or take regular medicines? Check with your GP or pharmacist first.
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View productComparing products? Our best magnesium glycinate supplements compared lists elemental magnesium per dose for nine UK options, and the benefits of magnesium sets out what magnesium can and can’t claim.
Sources 11
- NHS. Vitamins and minerals: others (magnesium).
- NHS. Diarrhoea and vomiting.
- NHS. Levothyroxine.
- NHS. How and when to take alendronic acid.
- NIH Office of Dietary Supplements. Magnesium: fact sheet for health professionals.
- European Food Safety Authority. Overview on tolerable upper intake levels.
- MHRA. Proton pump inhibitors in long-term use: reports of hypomagnesaemia. Drug Safety Update.
- Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register.
- Schuster J et al. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nature and Science of Sleep, 2025.
- Schuette SA et al. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN, 1994.
- Aal-Hamad AH et al. Hypermagnesemia in clinical practice. Medicina (Kaunas), 2023.
This guide is general information, not medical advice. Evopure makes the Magnesium Glycinate Sleep Complex.
