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Calcium
What Calcium 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
The main mineral of bone; also needed for muscle and nerve signalling.
What the evidence supports
ODS: with vitamin D, reduces bone loss and fracture risk in older adults.
Dose and timing
RDA: 1000 mg (19-50), women over 50 and men over 70: 1200 mg per day. Split doses (absorbed better in amounts of 500 mg or less); carbonate needs stomach acid, citrate does not.
Cautions
Food first — dairy, fortified drinks, greens. Supplements are for the gap, and some studies link very high doses to kidney stones.
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 — Calcium fact sheet · checked 2026-09-03
Frequently asked questions
What does Calcium do?
The main mineral of bone; also needed for muscle and nerve signalling.
Does Calcium work?
ODS: with vitamin D, reduces bone loss and fracture risk in older adults.
How much calcium should I take?
RDA: 1000 mg (19-50), women over 50 and men over 70: 1200 mg per day. Split doses (absorbed better in amounts of 500 mg or less); carbonate needs stomach acid, citrate does not.
Is Calcium safe?
Food first — dairy, fortified drinks, greens. Supplements are for the gap, and some studies link very high doses to kidney stones. 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.
Magnesium
RDA: men 400-420 mg, women 310-320 mg per day.
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.
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