Calcium
Supplement
mineral
bone & joint
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Bones and teeth · normal muscle and nerve function
When to take
With food · ≤500 mg at a time · 4 h from levothyroxine
Take with
Vitamin D (required for uptake) · citrate works without food
Pros & cons
Pros
- RDA 1,000 mg a day (19–50); food counts
- HSA allows bone, teeth, muscle and nerve claims
- With vitamin D, raised bone density in older adults
Cons
- Fracture prevention: trial results are mixed
- Carbonate causes more gas and constipation than citrate
- Supplements linked to kidney stones · heart data mixed
Sources
- NIH ODS — Calcium Fact Sheet for Health Professionals (updated June 22, 2026; read via archive.org capture, see verify_notes) — Table 1 RDAs; Introduction · read 2026-08-27
what it says
“19–50 years 1,000 mg … 51–70 years 1,000 mg 1,200 mg … >70 years 1,200 mg … Calcium makes up much of the structure of bones and teeth … Vitamin D is required for calcium to be absorbed in the gut by active transport”
- NIH ODS — Calcium Fact Sheet for Health Professionals (updated June 22, 2026; read via archive.org capture, see verify_notes) — Sources of Calcium — Dietary supplements (absorption) · read 2026-08-27
what it says
“absorption of calcium supplements is greater when they are taken with food … Calcium citrate is less dependent on stomach acid for absorption than calcium carbonate … Absorption from supplements is highest with doses of 500 mg or less”
- NIH ODS — Calcium Fact Sheet for Health Professionals (updated June 22, 2026; read via archive.org capture, see verify_notes) — Sources of Calcium — Dietary supplements (side effects) · read 2026-08-27
what it says
“gastrointestinal side effects, including gas, bloating, constipation … Calcium carbonate appears to cause more of these side effects than calcium citrate, especially in older adults who have lower levels of stomach acid”
- NIH ODS — Calcium Fact Sheet for Health Professionals (updated June 22, 2026; read via archive.org capture, see verify_notes) — Calcium and Health — Bone health in older adults · read 2026-08-27
what it says
“supplementation with calcium alone or a combination of calcium and vitamin D increases BMD in older adults … whether these BMD increases were clinically significant is not clear … research on the use of calcium supplementation to prevent fractures … are mixed”
- NIH ODS — Calcium Fact Sheet for Health Professionals (updated June 22, 2026; read via archive.org capture, see verify_notes) — Health Risks from Excessive Calcium; Table 3 ULs · read 2026-08-27
what it says
“19–50 years 2,500 mg … 51–70 years 2,000 mg … >70 years 2,000 mg … The ULs for calcium … are based on observational evidence from the WHI showing a link between higher intakes of supplemental calcium … and a greater risk of kidney stones”
- NIH ODS — Calcium Fact Sheet for Health Professionals (updated June 22, 2026; read via archive.org capture, see verify_notes) — Calcium and Health — Cardiovascular disease · read 2026-08-27
what it says
“the use of calcium supplements might actually increase the risk of cardiovascular disease, while other studies have found no link … calcium intakes that do not exceed the UL are safe "from a cardiovascular standpoint."”
- NIH ODS — Calcium Fact Sheet for Health Professionals (updated June 22, 2026; read via archive.org capture, see verify_notes) — Interactions with Medications · read 2026-08-27
what it says
“dolutegravir 2 hours before or 6 hours after taking calcium supplements … avoid taking levothyroxine within 4 hours … Long-term use of lithium … can lead to hypercalcemia … quinolone antibiotics … can reduce the absorption of quinolones … 2 hours before or 2 hours after”
- FDA — Daily Value on the Nutrition and Supplement Facts Labels, Reference Guide: Daily Values for Nutrients (content current as of 03/05/2024) · read 2026-08-27
what it says
“DVs are the recommended amounts of nutrients to consume or not to exceed each day … Calcium … 1300mg”
- HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020, January 2026 — clause 4.8, Table 5 Minerals Limits + List of Health Claims · read 2026-08-27
what it says
“HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits … Calcium 1200 mg … normal teeth • Calcium … normal muscle function • Calcium … normal neurotransmission • Calcium … Maintain/support bone health • Boron, calcium, magnesium, manganese, phosphorus, zinc”
- HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines GL-CHPB-1-012 Rev. No. 001, October 2025 — Annex A row 17 · read 2026-08-27
what it says
“17. Calcium Restricted use in HS and TM … When for oral use by general adult population, the maximum recommended daily dose should not provide more than 1200mg”
- iHerb Singapore — category page Calcium (Minerals), default order, 414 results · read 2026-08-27
what it says
“California Gold Nutrition, Magnesium Chelate with Calcium … 21st Century, Calcium Magnesium Zinc + D3 … Life Extension, Bone Restore, Calcium Supplement with Vitamin K2 … Nature's Bounty, Calcium Magnesium Zinc with Vitamin D3 … NOW Foods, Calcium & Magnesium, 250 Tablets”
- NIH ODS — Iron Fact Sheet for Consumers (updated August 17, 2023) — Does iron interact with medications or other dietary supplements? · read 2026-08-29
what it says
“Calcium might interfere with iron absorption. Taking calcium and iron supplements at different times of the day might prevent this problem.”
Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.