Product verdict
NOW Bone Calcium
14 ingredients on the label. None of them reach an amount we’ve seen work for anything we track.
Nothing in here reaches an amount we’ve seen work.
That isn’t proof it does nothing — it’s the honest limit of what we can tell you.
Supplement Facts
Serving Size 2 Tablet(s)
Servings Per Container 60
† Daily Value not established, or not stated on this label.
Worth knowing about this bottle
Magnesium with Zinc
Very high doses of zinc from supplements can interfere with magnesium absorption and disrupt the body's magnesium balance. This has only been demonstrated at zinc doses far above typical supplement amounts.
What to do: Only a concern at very high zinc doses (142 mg/day and up), well beyond a standard 15-30 mg zinc supplement. Not relevant for typical multivitamin or standalone zinc use.
Calcium with Phosphorus
High-dose calcium supplements can bind to phosphorus in the digestive tract and meaningfully reduce how much phosphorus the body absorbs. This is well documented but mainly relevant at high supplemental calcium doses, not typical dietary calcium intake.
What to do: Not a concern for most healthy people, since typical Western diets are phosphorus-rich. This is actually used medically (calcium carbonate as a phosphate binder) in kidney disease — don't attempt to manage phosphorus levels this way without medical supervision.
Zinc with Copper (Bisglycinate)
Taking high doses of zinc regularly can lower your body's copper levels over time. This is a well-known issue with long-term high-dose zinc supplementation or excessive use of zinc-containing denture creams.
What to do: If taking zinc supplements at doses well above the RDA for extended periods, watch for signs of copper deficiency or keep zinc intake near established upper limits (40 mg/day for adults).
Calcium with Zinc likely, not settled
In a controlled study of postmenopausal women, adding extra calcium to the diet modestly reduced how much zinc the body absorbed and retained over time. The effect was real but small, and high calcium intake has not been clearly linked to zinc deficiency in the general population.
What to do: People with low dietary zinc intake (e.g., vegetarians, older adults) who also take high-dose calcium may want to take large calcium doses at a different time than zinc-containing foods or supplements.
Vitamin D3 with Calcium likely, not settled
The pairing is standard and works, but it is not free of risk: in the Women’s Health Initiative, women taking calcium with vitamin D had more kidney stones than those on placebo.
What to do: Worth knowing if you have had a kidney stone. Otherwise the pairing remains the standard one; do not stop it on the strength of this alone.
Vitamin D3 and Magnesium work better together
Magnesium is needed to convert vitamin D into its active form. Without enough magnesium, vitamin D supplements may work less well because the enzymes that activate vitamin D can't function properly.
Vitamin D3 and Calcium work better together
Vitamin D significantly enhances calcium absorption in the intestine, improving bone health outcomes.
Vitamin D3 and Magnesium Glycinate work better together
Magnesium is required for vitamin D metabolism. Deficiency in either impairs the other's function.
2 present in trace amounts
Far under everything studied. No trial speaks to what this much does.
- Supports frequent colds — dose is 80% short of the 2000–4000 IU tested.
- Supports slow recovery — dose is 80% short of the 2000–4000 IU tested.
- Some evidence for chronic fatigue — dose is 80% short of the 2000–4000 IU tested.
- Some evidence for hair thinning — dose is 80% short of the 2000–4000 IU tested.
- Some evidence for chronic inflammation — dose is 80% short of the 2000–4000 IU tested.
- Some evidence for joint pain — dose is 77% short of the 3–9 mg tested.
Label read from the NIH Dietary Supplement Label Database. Formulations change — check the panel on the bottle in your hand. Check a different product.