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Magnesium
What Magnesium is, what the NIH ODS fact sheet says the evidence supports, typical doses, timing, and the cautions that come with it.
Supplements are not medicines and this page is not medical advice. Doses that help one person can harm another — with medicines, kidney or liver conditions, pregnancy, or before surgery, talk to a clinician before starting anything. More is not better.
What it is
A mineral in hundreds of enzyme reactions: muscle and nerve function, energy, bone.
What the evidence supports
ODS: supplements correct deficiency; high-dose supplementation is also studied for migraine (under medical supervision).
Dose and timing
RDA: men 400-420 mg, women 310-320 mg per day. With food to reduce stomach upset; some people prefer evening.
Cautions
Citrate and glycinate forms are often better tolerated than oxide. Doses above the UL (350 mg from supplements) can cause diarrhoea.
Interactions are the hidden risk: supplements can change how medicines work and vice versa. Give your clinician the full list before anything else.
Source: NIH Office of Dietary Supplements — Magnesium fact sheet · checked 2026-09-03
Frequently asked questions
What does Magnesium do?
A mineral in hundreds of enzyme reactions: muscle and nerve function, energy, bone.
Does Magnesium work?
ODS: supplements correct deficiency; high-dose supplementation is also studied for migraine (under medical supervision).
How much magnesium should I take?
RDA: men 400-420 mg, women 310-320 mg per day. With food to reduce stomach upset; some people prefer evening.
Is Magnesium safe?
Citrate and glycinate forms are often better tolerated than oxide. Doses above the UL (350 mg from supplements) can cause diarrhoea. And the standing rule: tell your clinician everything you take — supplements interact with medicines.
Creatine
Studied doses: 3-5 g per day; loading protocols use about 20 g/day in 4 doses for 5-7 days.
Vitamin D
RDA: 600 IU (15 mcg) to age 70, then 800 IU (20 mcg). UL 4000 IU.
Omega-3s (EPA/DHA)
No RDA for EPA/DHA; ALA: men 1.6 g, women 1.1 g per day. Many products supply 250-500 mg combined EPA+DHA per day.
Melatonin
Studied doses commonly 0.5-5 mg, taken 30-60 minutes before bed.
Iron
RDA: men 8 mg, women 19-50 18 mg, pregnancy 27 mg per day.
Vitamin B12
RDA: 2.4 mcg per day.
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