NutriStack
Hydrochlorothiazide and Vitamin D2, a caution.
Hydrochlorothiazide reduces urinary calcium excretion, and Vitamin D2 can increase calcium absorption after conversion to active vitamin D metabolites. The concern is hypercalcemia when Vitamin D2 is taken in high doses or combined with high calcium intake. People with kidney disease, hyperparathyroidism, granulomatous disease, or dehydration are at higher risk.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
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At a glance
- Substances
- Hydrochlorothiazide and Vitamin D2
- Pair type
- Caution
- Evidence (highest tier)
- Emerging
- 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 · Emerging evidence
Caution
What is happening. Hydrochlorothiazide reduces urinary calcium excretion, and Vitamin D2 can increase calcium absorption after conversion to active vitamin D metabolites. The concern is hypercalcemia when Vitamin D2 is taken in high doses or combined with high calcium intake. People with kidney disease, hyperparathyroidism, granulomatous disease, or dehydration are at higher risk.
Mechanism. Thiazide diuretics increase distal calcium reabsorption, while Vitamin D2 repletion increases intestinal calcium uptake. The combined effect can raise serum calcium in susceptible patients.
Recommendation. Do not combine hydrochlorothiazide with high-dose Vitamin D2 without a monitoring plan. Ask for serum calcium monitoring after starting or changing Vitamin D2, especially if you also take calcium or have a history of kidney stones.
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
- 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
Stack Score
How this pair moves the number.
Effect on the composite score
If both Hydrochlorothiazide and Vitamin D2 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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