Calcium Formate

MineralCalcium salt

What is it

Calcium formate is the calcium salt of formic acid (Ca(HCOO)2). It is used industrially in animal feed and cement, and occasionally appears in supplements as a calcium source or preservative-related ingredient.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Calcium supplementation

Limited Evidence

Calcium formate is bioavailable and contributes to total calcium intake, but it has been studied much less than calcium carbonate, citrate, or malate, so head-to-head efficacy data are limited.

How it works

In the gut, calcium formate dissociates to release calcium ions and formate. Calcium absorption proceeds through the standard active (vitamin D-dependent) and passive paracellular pathways. Formate is a small organic anion that participates in one-carbon metabolism; at supplement doses it is metabolized to CO2 and water without notable accumulation. As a calcium supplement source, calcium formate has been studied less than carbonate, citrate, or malate. Its calcium content is moderate (approximately 30% by weight). It is more commonly encountered in livestock nutrition than human supplements.

Dosage

There is no Recommended Dietary Allowance for calcium formate specifically. Total calcium intake from all sources should reach the adult RDA of 1000-1200 mg/day, with a tolerable upper intake level of 2000-2500 mg/day from all sources combined. Supplement doses providing 200-600 mg elemental calcium are typical.

When and how to take it

Calcium formate, like calcium citrate, can be taken with or without food. Doses above 500 mg of elemental calcium should be split throughout the day for better absorption. Separate from iron, zinc, and certain antibiotics by 2-4 hours.

1 commercial form

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Calcium formate

Less common in human supplements than carbonate or citrate; more typical in animal feed.

Bioavailability appears comparable to other soluble calcium salts.

Safety

Generally well tolerated at supplement doses. Side effects mirror other calcium supplements: constipation, bloating, and rarely kidney stones at high intakes. Formate itself can be toxic at much higher doses (as in methanol poisoning) but supplement-level exposure is far below toxic thresholds.

Who should be cautious

People with hypercalcemia, hyperparathyroidism, kidney stones, or chronic kidney disease should consult a clinician before adding calcium supplements. Pregnancy and breastfeeding generally use the standard calcium RDA. People on cardiac glycosides should monitor calcium status.

Interactions

Reduces absorption of tetracycline and quinolone antibiotics, bisphosphonates, and levothyroxine (take 2-4 hours apart). Excessive calcium can interfere with iron, zinc, and magnesium absorption.

Food sources

Dairy (milk, yogurt, cheese)

Amount
200-450 mg per serving
%DV
20%

Fortified plant milks

Amount
300 mg per cup
%DV
25%

Tofu (calcium-set)

Amount
200-400 mg per 1/2 cup
%DV
25%

Frequently asked questions

How does calcium formate compare to calcium carbonate?⌄

Calcium carbonate is more concentrated (40% elemental calcium vs. ~30% for formate) and far more thoroughly studied in humans. Calcium formate is bioavailable but less common in consumer supplements.

Is the 'formate' part safe?⌄

Yes, at supplement doses. Formate is a normal intermediate in human metabolism and the amounts involved are far below any toxic threshold.

References

Calcium Formate on Wikidata — Wikidata link

Calcium Formate on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Calcium Formate (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.