NutriStack
Hydrochlorothiazide and Vitamin D3, a caution.
Hydrochlorothiazide can raise serum calcium by reducing urinary calcium loss, while Vitamin D3 increases intestinal calcium absorption. Standard Vitamin D3 doses are often tolerated, but high-dose supplementation can increase hypercalcemia risk in people with kidney disease, hyperparathyroidism, sarcoidosis, or high calcium intake. The risk is mainly a lab and dose-monitoring issue rather than a timing issue.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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At a glance
- Substances
- Hydrochlorothiazide and Vitamin D3
- 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. Hydrochlorothiazide can raise serum calcium by reducing urinary calcium loss, while Vitamin D3 increases intestinal calcium absorption. Standard Vitamin D3 doses are often tolerated, but high-dose supplementation can increase hypercalcemia risk in people with kidney disease, hyperparathyroidism, sarcoidosis, or high calcium intake. The risk is mainly a lab and dose-monitoring issue rather than a timing issue.
Mechanism. Hydrochlorothiazide increases renal tubular calcium reabsorption. Vitamin D3 is converted to active vitamin D metabolites that increase intestinal calcium absorption, so both pathways can raise serum calcium.
Recommendation. Use conservative Vitamin D3 dosing unless your clinician is monitoring calcium and 25-hydroxyvitamin D. If you take hydrochlorothiazide plus daily or high-dose Vitamin D3, ask whether serum calcium should be checked after starting or changing doses.
Sources (2)
- Chandler PD, Scott JB, Drake BF, Ng K, Forman JP, Chan AT, et al. Risk of hypercalcemia in blacks taking hydrochlorothiazide and vitamin D. Am J Med. 2014;127(8):772-778. PMID 24657333
- 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
Stack Score
How this pair moves the number.
Effect on the composite score
If both Hydrochlorothiazide and Vitamin D3 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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