Calcium Citrate with D3 and K2

Description

Calcium citrate with vitamin D3 and vitamin K2 in the same tablet, with all three amounts printed on the panel instead of two of them. Calcium citrate is the salt of citric acid, and the first thing to understand about it is the weight arithmetic: the citrate part of the molecule accounts for most of the mass, so elemental calcium is about 21 percent of the compound weight. A tablet listing 1,000 mg of the salt is delivering roughly 210 mg of calcium.

The three amounts, and the arithmetic

Why calcium citrate costs more per milligram than carbonate

Because you are buying more tablet for the same calcium. Carbonate is denser in elemental terms, so a carbonate tablet reaching 500 mg of calcium is physically smaller than a citrate tablet doing the same job. That is the trade, and it is why the elemental figure goes in the main amount column on the minerals page with the compound weight printed underneath it.

The published absorption work is what people buy the citrate form for. Studies measuring calcium absorption have found citrate absorbed without requiring gastric acid, where carbonate absorption measured lower when taken away from food or in people with reduced stomach acid. That describes what those studies measured. It is not a claim about this bottle.

Why D3 and K2 are in the same tablet

Both are fat soluble vitamins that the calcium literature keeps company with, and putting them in one tablet removes two bottles from a cupboard. D3 is quoted in both IU and micrograms here because the conversion catches people out: 1,000 IU is 25 micrograms, so two labels with very different front numbers can hold the same amount.

K2 as MK-7 is the longer chain form, distinct from MK-4, and the panel names which one. Anyone taking warfarin or another vitamin K antagonist should treat any added vitamin K as a change worth discussing with whoever manages that prescription.

How much calcium citrate is worth taking at once

Absorption studies on calcium consistently measure a falling percentage as the single dose rises, and the convention in that literature is to split intakes above roughly 500 mg of elemental calcium. That is why multi tablet servings are normal across this category, and why units per serving sits next to servings per container on every listing here. Taking a whole day of calcium citrate in one swallow is the common mistake, and it is one a label almost never addresses.

Iron, thyroid medicine and the other timing notes

Calcium competes with iron and with zinc for absorption, which is why iron bottles carry a timing instruction and why the women’s formulas with iron on this site state it on the panel. Calcium citrate can be taken with or without a meal, where the published work measured carbonate as needing stomach acid and therefore food. Anyone on a thyroid medicine or a tetracycline antibiotic should separate the two by several hours. That is a pharmacy note rather than a product claim, and a pharmacist is the right person to confirm it.

Reference intakes, from a source that sells nothing

The NIH calcium fact sheet gives recommended intakes by age and sex, the calcium content of common foods, the upper intake level, and a summary of what supplementation trials have measured. Reading it before buying any calcium product is the cheapest research you can do, and it will tell you whether your diet already covers the gap.

Testing

Every lot of calcium citrate tablets is assayed by an independent laboratory for all three actives, with heavy metals screened as well, which matters more in this aisle than most because mineral salts are mined material. Under strength lots are withdrawn from sale and the failing certificate stays on the public page, as set out in why we publish the batch that failed. Your certificate is linked above.