Last updated: October 2026
Magnesium may help some PMS symptoms, but the evidence is limited. Small trials found it eased bloating and fluid retention after two cycles, and mood symptoms in another, while the NHS says there’s not much evidence that supplements work. If you try it, take 200 to 250mg a day for at least two to three cycles.
Below: what the trials actually found, which type of magnesium to choose, how much and when, magnesium with vitamin B6, foods that help, and when to see your GP.
What the research shows
| Study | Who and what | What it found |
|---|---|---|
| Italy, 1991 | 32 women with PMS; magnesium three times a day in the second half of the cycle | Better mood scores than placebo by the second month |
| University of Reading, 1998 | 38 women; 200mg magnesium a day for two cycles | No difference in month one; less bloating, swelling, breast tenderness and weight gain in month two |
| University of Reading, 2000 | 44 women; 200mg magnesium, 50mg vitamin B6, both, or placebo, one cycle each | Magnesium plus B6 eased anxiety-type symptoms; magnesium alone made no significant difference over one cycle |
| Cochrane review, 2016 | 27 trials of supplements for period pain | No high-quality evidence for any supplement, including magnesium |
Two patterns stand out. Benefits showed up after the second cycle, not the first, and the trials were small. The NHS lists magnesium among supplements that “may help with PMS” but notes there isn’t much evidence that they work.
Which PMS symptoms might it help?
- Bloating and fluid retention: the clearest trial result. Magnesium contributes to electrolyte balance. See magnesium for bloating.
- Mood and irritability: one small trial; magnesium contributes to normal psychological function.
- Tiredness: magnesium contributes to the reduction of tiredness and fatigue.
- Cramps: magnesium contributes to normal muscle function, but trial evidence for period pain is weak. See magnesium for cramps.
- Sleep: many people take magnesium as part of an evening routine in the days before a period.
Best type of magnesium for PMS
| Type | For PMS |
|---|---|
| Glycinate (bisglycinate) | Gentle on the stomach, popular in the evening |
| Citrate | Well absorbed; can loosen stools, which some find helpful if PMS brings constipation |
| Oxide | Used in the Reading trials; cheap but less well absorbed and more likely to upset the stomach |
Our Magnesium Glycinate Sleep Complex combines bisglycinate and citrate with glycine, L-theanine and botanicals, giving 148mg of magnesium per serving as a warm evening drink. Compare forms in magnesium glycinate vs citrate vs threonate.
How much and when to take it
- Amount: trials mostly used about 200mg of magnesium a day. The NHS says 400mg or less a day from supplements is unlikely to cause harm.
- When in your cycle: some trials used it only in the second half of the cycle, others every day. Daily is simpler and keeps levels steady.
- Time of day: the evening suits most people. See best time to take magnesium.
- How long: give it at least two to three cycles before deciding, and keep a symptom diary so you can tell.
Speak to your GP first if you have kidney problems, and ask a pharmacist about timing if you take antibiotics or other regular medicines.
Magnesium and vitamin B6
The 2000 trial found magnesium worked better alongside vitamin B6. Vitamin B6 contributes to the regulation of hormonal activity. But the trial used 50mg of B6, and the NHS advises no more than 10mg a day from supplements unless a doctor advises more, because long-term high doses can cause nerve damage. Many multivitamins already contain B6, so check the total.
Magnesium-rich foods
Most women need 270mg a day, and food is the best place to start: pumpkin seeds, almonds, spinach and other leafy greens, wholegrains, beans and lentils, and dark chocolate.
Other things that help PMS
- Regular exercise, especially in the week before a period.
- Smaller, more frequent meals to keep energy steady.
- Less salt, caffeine and alcohol in the second half of your cycle.
- Regular sleep and stress management, such as yoga or relaxation exercises.
- Tracking symptoms for two to three cycles, which also helps your GP.
Some people also try CBD. See CBD for PMS and periods and magnesium for women.
When to see your GP
See your GP if PMS affects your work, relationships or daily life, if self-help hasn’t helped after a few cycles, or if you have very low mood or thoughts of self-harm before your period. That could be premenstrual dysphoric disorder (PMDD), which has effective treatments. Very heavy or painful periods should also be checked, as they can have other causes such as endometriosis.
FAQs
Does magnesium help with PMS?
It may help some women, especially with bloating and fluid retention, but the trials are small and the NHS says there isn’t much evidence. Give it two to three cycles.
How much magnesium should I take for PMS?
Trials mostly used about 200mg a day. Keep total supplement magnesium to 400mg a day or less, as the NHS advises.
What is the best magnesium for PMS?
There are no head-to-head trials. Glycinate is gentle on the stomach and popular in the evening; citrate is well absorbed. Pick one you’ll take every day.
When should I take magnesium for PMS?
Daily, usually in the evening, is simplest. Some trials used it only in the second half of the cycle.
How long does magnesium take to work for PMS?
In trials, benefits appeared in the second cycle, not the first. Keep a symptom diary for two to three cycles.
Can I take magnesium and vitamin B6 together?
Yes. One trial found the combination worked better, but keep vitamin B6 from supplements to 10mg a day unless your doctor advises more.
Sources
- NHS. PMS (premenstrual syndrome).
- NHS. Vitamins and minerals: magnesium.
- NHS. Vitamins and minerals: vitamin B6.
- Facchinetti F et al. Oral magnesium successfully relieves premenstrual mood changes. Obstet Gynecol, 1991.
- Walker AF et al. Magnesium supplementation alleviates premenstrual symptoms of fluid retention. J Womens Health, 1998.
- De Souza MC et al. A synergistic effect of 200mg magnesium plus 50mg vitamin B6 for anxiety-related premenstrual symptoms. J Womens Health Gend Based Med, 2000.
- Pattanittum P et al. Dietary supplements for dysmenorrhoea. Cochrane Database Syst Rev, 2016.
