Is Calcium Safe with Chlorthalidone?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Do not routinely add high-dose calcium supplements while on chlorthalidone without physician guidance. Thiazide-type diuretics reduce urinary calcium loss, which may be beneficial for osteoporosis but can elevate serum calcium if combined with high-dose calcium or vitamin D supplementation. Have calcium levels checked annually.
Why this interaction occurs
Unlike loop diuretics, thiazide-type diuretics including chlorthalidone increase calcium reabsorption in the distal convoluted tubule, reducing urinary calcium excretion. This hypocalciuric effect is beneficial for bone density but can cause hypercalcemia when patients simultaneously take high-dose calcium supplements or active vitamin D analogs, particularly in those with primary hyperparathyroidism or granulomatous disease.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 13,302 reports mentioning Chlorthalidone. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Chlorthalidone + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Calcium interactions → · All Chlorthalidone interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.