Magnesium dosage for PMS and PMDD: how much to take

Trials on magnesium and PMS settled on two doses: 200 mg a day, or 360 mg a day. The form differed too, magnesium oxide in the lower-dose trials, magnesium pyrrolidone carboxylate in the higher-dose ones.

In the trials that tracked results across two cycles, magnesium took about two months to show its clearest effect. The one-cycle 2000 trial, which combined magnesium with vitamin B6, found a modest effect within a single cycle. Of these four trials, three found magnesium eased symptoms on its own; the fourth found a benefit only when combined with vitamin B6, not from magnesium alone.

None of the trials above used magnesium glycinate, and none diagnosed PMDD with daily symptom tracking across two cycles, the method DSM-5-TR requires. They studied PMS, diagnosed with the Moos Menstrual Distress Questionnaire, a broader and looser measure.

That distinction matters because PMS and PMDD aren't interchangeable. If you're looking for a dose tested specifically in women with a confirmed PMDD diagnosis, this body of research doesn't have one.

In practice, the 200 to 360 mg range from PMS trials is the closest evidence available. Glycinate is a well-absorbed form of magnesium, so it's reasonable to think the same 200 to 360 mg range would apply, though this hasn't been tested directly.

For PMDD itself, guidelines point to treatments with trial support behind them:

• SSRIs, which some people take only in the luteal phase
• Certain hormonal contraceptives
• CBT

A doctor decides which fits. See magnesium for PMDD and supplements for PMDD for how magnesium fits alongside those.

Trials used both schedules, and both showed results, just not until the second month.

• Daily, all month, 200 mg: easier to keep up since you're not watching the calendar. Took two full cycles before fluid-related symptoms like bloating eased in one trial.
• Luteal phase only, 360 mg from day 15 to your period: matches the window when estrogen and progesterone are dropping. Improved overall symptom scores and mood by the second month in two trials from the same research group.

Neither schedule showed much in the first month in the trials that measured it, so give whichever one you try at least two cycles before deciding it isn't working. More on timing is in how long magnesium takes to work.

Niyora is a PMS and PMDD support app. While you wait those two months to see if magnesium is helping, Niyora's estimated PMS window can help you notice whether your symptoms are actually easing cycle to cycle.

None of the trials above tested doses higher than 360 mg a day, so that's the upper edge of what's actually been studied for PMS.

Above that, oral magnesium is more likely to cause:

• Loose stools or diarrhea
• Stomach cramping or nausea

These usually ease once you lower the dose or take it with food. More detail, including the mood-related side effects some people report, is on magnesium side effects.

The trials behind these numbers didn't separate PMS from PMDD the way guidelines define it now. They used the Moos Menstrual Distress Questionnaire, a broad PMS measure, not the daily DSM-5-TR tracking that confirms PMDD.

In practice, most people use the same 200 to 360 mg range for either, since there's no separate PMDD dosing trial to point to. What does differ is the wider treatment plan: PMDD guidelines also include SSRIs, some hormonal contraceptives, and CBT, options magnesium doesn't replace. Read more on PMS treatment and magnesium for PMS for how it fits into that wider picture.

If you've tried magnesium for two full cycles with no change, or your mood symptoms take over a week of most months, see a GP or gynecologist and bring two months of daily notes.