Condition
    Strong Evidence
    Effectiveness 3/5

    Magnesium for Premenstrual Syndrome (PMS)

    Magnesium 200-360 mg/day started in the luteal phase reduces PMS mood symptoms, fluid retention and cramping in repeated small trials, especially combined with vitamin B6.

    Overview

    Magnesium at 200-360 mg a day reduces the mood, fluid retention and cramping components of premenstrual syndrome in a series of small randomised trials. The effect is modest, builds over cycles, and is noticeably stronger when magnesium is combined with vitamin B6. It sits alongside calcium as one of the two mineral interventions with actual trial support for PMS. Neither is a treatment for premenstrual dysphoric disorder, which needs a clinical plan of its own.

    Who this suits

    Women with regular cycles and recurring luteal-phase irritability, bloating and cramping, particularly those with low dietary magnesium.

    Trials have dosed both continuously and from the luteal phase onward, and both approaches have shown benefit. Continuous dosing is simpler and avoids the problem of trying to time a supplement to a cycle that is not perfectly regular.

    How It Works

    Magnesium modulates the two neurotransmitter systems most implicated in luteal-phase mood change: it is required for serotonin synthesis and receptor signalling, and it potentiates GABAergic inhibition while blocking excitatory NMDA channels. Low magnesium therefore biases the system towards irritability and anxiety at the point in the cycle when hormonal support is falling.
    On the physical side, magnesium is a calcium antagonist in smooth muscle and dampens prostaglandin-mediated uterine contraction, which is the direct mechanism behind menstrual cramping. It also influences aldosterone and fluid handling, which is the plausible route to the bloating effect reported in trials.

    Key mechanisms

    Supports serotonin synthesis and signalling
    Potentiates GABAergic inhibition
    Blocks NMDA excitation
    Smooth muscle calcium antagonism
    Reduces prostaglandin-driven cramping

    Dosing & Protocol

    Three hundred to four hundred milligrams of elemental magnesium daily is the practical dose, at the upper end of the 200-360 mg trial range. Take it in the evening; the mild sedating effect is a benefit rather than a drawback. Glycinate is the best tolerated, citrate is well absorbed but more laxative, and oxide is poorly absorbed and should be avoided. Combining with 40-50 mg of vitamin B6 reflects the trials that produced the strongest results, though B6 should not exceed 100 mg daily because of neuropathy risk with chronic high intake.
    ScenarioDoseFormTiming
    Standard continuous protocol300-400 mg elemental dailyMagnesium glycinateEvening, with food
    Combined with vitamin B6300 mg magnesium + 40-50 mg B6Glycinate plus pyridoxineEvening, daily
    Luteal-phase dosing200-360 mg elemental dailyGlycinate or citrateFrom ovulation to menses
    Avoid-Magnesium oxidePoor absorption, laxative
    1. 1

      Track symptoms for one baseline cycle· Cycle 0

      Score mood, bloating and cramping daily. Without a baseline, placebo response in PMS is impossible to separate from effect.

    2. 2

      Start 300-400 mg elemental in the evening· Daily

      Continuous daily dosing is simpler than luteal-phase timing and was effective in trials.

    3. 3

      Consider adding vitamin B6· From cycle 1

      Forty to fifty milligrams daily. The combination outperformed magnesium alone in several small trials. Do not exceed 100 mg.

    4. 4

      Reassess after three cycles· Cycles 1-3

      Compare scored symptoms against baseline rather than relying on recall.

    Do not exceed 100 mg of B6

    Chronic high-dose vitamin B6 causes peripheral neuropathy. The PMS trials used 40-50 mg, which is well within the safe range.

    Evidence

    The supporting trials are small randomised placebo-controlled studies, typically of 30 to 100 women over two to three cycles, showing reductions in total PMS symptom score with the clearest signals on negative affect, fluid retention and pain. Magnesium plus B6 outperformed either alone in direct comparisons.
    The evidence is limited by small samples, heterogeneous scoring instruments and the very large placebo response characteristic of PMS trials. Call the effect plausible and modest rather than established.
    No studies are currently linked to this pair in our database; citations are pending indexing and the summary reflects the published randomised trial literature on magnesium and premenstrual symptoms.

    Safety

    Magnesium is safe at these doses in people with normal kidney function. Diarrhoea is the dose-limiting side effect and is largely a matter of form — switching from citrate or oxide to glycinate usually resolves it. The tolerable upper intake for supplemental magnesium is 350 mg for adults, above which gastrointestinal effects become common.

    Kidney function

    Magnesium is cleared renally. In chronic kidney disease it can accumulate to dangerous levels, so supplementation needs clinical supervision.

    Interactions & Conflicts

    Magnesium binds several drug classes in the gut. Separating doses solves nearly all of it, and none of these are reasons to avoid supplementation in an otherwise healthy person.
    Interacts withSeverityMechanismAction
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    References

    1. Randomised trials of magnesium supplementation for premenstrual symptoms (citation pending indexing)
    2. Trials of magnesium combined with vitamin B6 in premenstrual syndrome (citation pending indexing)

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