NutriStack
Calcium and Chlorthalidone, a caution.
Chlorthalidone is thiazide-like and reduces urinary calcium loss, which can raise serum calcium. High-dose calcium supplements can add to that effect and increase hypercalcemia risk, especially with dehydration, kidney disease, hyperparathyroidism, or heavy calcium antacid use. Symptoms may include nausea, constipation, thirst, confusion, weakness, or kidney injury.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Calcium and Chlorthalidone
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. Chlorthalidone is thiazide-like and reduces urinary calcium loss, which can raise serum calcium. High-dose calcium supplements can add to that effect and increase hypercalcemia risk, especially with dehydration, kidney disease, hyperparathyroidism, or heavy calcium antacid use. Symptoms may include nausea, constipation, thirst, confusion, weakness, or kidney injury.
Mechanism. Thiazide and thiazide-like diuretics increase distal tubular calcium reabsorption and reduce urinary calcium excretion. Calcium supplementation increases absorbed calcium load, making hypercalcemia more likely in susceptible patients.
Recommendation. Avoid high-dose calcium while taking chlorthalidone unless your prescriber recommends and monitors it. If you need daily calcium, keep the dose within your target intake and ask whether serum calcium should be checked.
Sources (2)
- Wermers RA, Kearns AE, Jenkins GD, Melton LJ 3rd. Incidence and clinical spectrum of thiazide-associated hypercalcemia. Am J Med. 2007;120(10):911.e9-911.e15. PMID 17904464
- Desai HV, Gandhi K, Sharma M, Jennine M, Singh P, Brogan M. Thiazide-induced severe hypercalcemia: a case report and review of literature. Am J Ther. 2010;17(6):e234-e236. PMID 20068444
Stack Score
How this pair moves the number.
Effect on the composite score
If both Calcium and Chlorthalidone are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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