The form matters more than the dose, and most magnesium sold in supermarkets is the form that works least well. If you take one thing from this: magnesium oxide is cheap because it is poorly absorbed, and its main reliable effect is loosening your bowels. Glycinate and citrate are the ones worth your money.
How much you actually need
The recommendation for women over 30 is 320 mg a day, from food and supplements combined. Average intake commonly sits below that, which is the honest case for supplementing — not that magnesium fixes perimenopause, but that a lot of people are short of a nutrient doing real work across muscle, nerve, blood sugar and bone.
Food first is not a platitude here: pumpkin seeds, almonds, spinach, black beans, dark chocolate and wholegrains all carry meaningful amounts.
The forms, and what each is for
- Magnesium glycinate (bisglycinate). Magnesium bound to glycine. Well absorbed, gentle on the stomach, and the form usually chosen where sleep or calm is the goal — partly because glycine itself has a role in sleep onset. This is the one to start with for most people.
- Magnesium citrate. Well absorbed and effective, with a laxative effect that rises with dose. Useful if constipation is also a problem; irritating if it is not.
- Magnesium oxide. High magnesium by weight, poorly absorbed. It is what makes cheap supplements cheap, and it is functionally a laxative.
- Magnesium malate. Well tolerated, sometimes chosen for fatigue, though the evidence for that specific use is thin.
- Magnesium L-threonate. Marketed for the brain on the basis that it crosses into the central nervous system more readily. Interesting mechanism, very little human evidence, considerably more expensive.
- Epsom salts (magnesium sulfate). Pleasant in a bath. The evidence that meaningful magnesium gets in through your skin is not there.
What the evidence actually supports
Graded honestly, because magnesium is marketed well beyond what the trials show:
- Constipation. Reliable, and the least glamorous use. Citrate and oxide both work.
- Migraine. The strongest case in this list, with enough support that it appears in headache guidance.
- Sleep. Small trials with mixed quality. The signal is not nothing, the safety profile is good, and many women are genuinely short — a reasonable thing to try rather than a treatment.
- Anxiety and low mood. Same picture: small, mixed, plausible.
- Perimenopause specifically. Thin. Most of what you read extrapolates from general magnesium research rather than from trials in perimenopausal women, and it is worth knowing that is what is happening.
Practical notes
- Start at the lower end. Supplemental magnesium is commonly taken at 200 to 400 mg; more is not better and the excess mostly reaches your bowels.
- Evening suits most people, particularly for glycinate.
- Split the dose if a single one upsets your stomach.
- Space it from certain medicines. Magnesium can interfere with the absorption of some antibiotics and with bisphosphonates. A couple of hours apart is the usual advice — check with a pharmacist.
- Kidney disease changes this entirely. If your kidneys do not clear magnesium normally, supplementing is a medical decision, not a shelf one.
Reading the label
The number on the front is often the weight of the whole compound, not the elemental magnesium in it. "1000 mg magnesium citrate" is not 1000 mg of magnesium — it is closer to 160. Look for elemental magnesium per serving, and check how many capsules a serving is.
That is the standard we hold ourselves to: the MYNDR evening formula carries 200 mg of magnesium glycinate, printed on the label, alongside glycine at the 3 g dose used in the sleep-onset research. It is there for the night-time half of the system rather than as a magnesium supplement in its own right — if magnesium alone is what you are after, a single-ingredient glycinate is cheaper and we would say so.
The short version
- 320 mg a day is the recommendation for women over 30, food included.
- Glycinate for sleep and tolerance; citrate if constipation is also a problem; skip oxide.
- Threonate is expensive and under-evidenced. Epsom salts do not meaningfully absorb.
- Best evidence is for migraine and constipation. Sleep and mood are plausible but small.
- Check elemental magnesium per serving, not the compound weight on the front.
- Kidney disease, or antibiotics and bisphosphonates: check with a pharmacist first.
This article is general information, not medical advice. Talk to a clinician or pharmacist about your own symptoms, history and any supplement taken alongside prescribed medication. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
