Calcium is the body's most abundant mineral, with around 99% stored in the bones and teeth and the remaining fraction doing vital work in muscle contraction, nerve signalling and blood clotting. Our calcium collection brings together well-absorbed forms — citrate, hydroxyapatite and marine-source calcium — alongside the cofactors that decide where calcium actually ends up.

How calcium works — and why the cofactors matter

Calcium does not act alone. To be absorbed from the gut it needs vitamin D; to be deposited into bone rather than soft tissue it needs vitamin K2, which activates the proteins that escort calcium into the skeleton and help keep it out of arteries; and it needs magnesium, which works alongside calcium in muscle and nerve function and helps activate vitamin D. This is the key insight: taking high-dose calcium in isolation is not just less effective, it can be counterproductive — the goal is to get calcium into bone, and that requires the supporting team.

What to look for — the form question

Calcium carbonate is the most concentrated and economical form, but it relies on stomach acid and should be taken with food, which makes it less suitable for older adults or anyone on acid-suppressing medication. Calcium citrate is well absorbed with or without food and is gentler on digestion. Microcrystalline hydroxyapatite (a bone-derived form) and marine plant-source calcium supply calcium within a natural mineral matrix. Whichever you choose, look for added vitamin D and ideally K2, and split larger doses across the day, as the gut absorbs calcium best in amounts of around 500mg at a time.

Who may benefit

Post-menopausal women, older adults, people with low dairy intake or on plant-based diets, and those whose practitioner has flagged low bone density commonly supplement calcium — ideally as part of a broader bone-support approach rather than in isolation.

Frequently asked questions

Which form of calcium is best absorbed?
Calcium citrate is well absorbed with or without food and suits most people, especially older adults and those on acid-reducing medication. Carbonate is more concentrated but needs food and good stomach acid. The best form is the one your body tolerates and absorbs.

Should I take calcium with vitamin D and K2?
Yes — vitamin D helps you absorb calcium and K2 helps direct it into bone rather than arteries. Magnesium is a useful partner too. This is why combined bone formulas are often preferable to calcium alone.

Can I take too much calcium?
Yes. Very high supplemental calcium without its cofactors has been linked to arterial and kidney concerns, so it is best to meet needs from diet first, keep supplemental doses moderate (around 500mg at a time), and pair with D, K2 and magnesium. Check with your healthcare professional.

Explore related ranges in our Bone Health, Vitamin D, Magnesium and Collagen collections.

Always read the label and follow the directions for use. Supplements are not a substitute for a balanced diet. If you have a medical condition, are pregnant or take medication, talk to your health professional.