What should you look at when choosing a calcium supplement?

Calcium is one of the categories where the number on the box most easily misleads.

Which number do you compare?

Calcium is present as a compound, so labels state the compound weight first with the elemental calcium in brackets — for example calcium carbonate 1,500 mg (provides calcium 600 mg).

The bracketed figure is the one to compare, not the larger number in front of it.

How do the forms differ?

Carbonate carries the highest proportion of calcium per unit weight, so tablets are smaller for the same amount. It relies on stomach acid, so it is usually suggested with food.

Citrate carries less per unit weight, so tablets are larger or more numerous, but it depends less on stomach acidity.

L-threonate carries less per unit weight again, and tends to appear in formulations built around being easy to take rather than high per tablet.

No form suits everyone. What can be compared is the elemental amount and how comfortable it is.

Is vitamin D included?

The annex to Thai Ministry of Public Health Notification No. 447 (B.E. 2566) states that vitamin D contributes to normal absorption of calcium and phosphorus. That is why many formulations include it.

Some also include magnesium or menaquinone-7. That is a matter of composition, to judge against what you are looking for.

How many tablets a day?

The body absorbs calcium more efficiently in amounts up to around 500 mg at a time, so a formulation delivering a large amount in one tablet is not automatically more convenient. Splitting across two occasions usually makes more sense.

What should it be spaced from?

Large amounts of calcium interfere with iron and zinc absorption. If you take those as well, separating them in time is easier than taking them together.

What should you check before buying?

The อย. food serial number, elemental calcium per serving, tablets per serving, expiry date, and price per unit of elemental calcium.

If you take prescription medication, speak to a doctor or pharmacist first.

Dietary supplements are not intended to prevent, treat or cure any disease.