The short answer
Vitamin D can raise blood calcium during hydrochlorothiazide treatment, although high calcium was uncommon in one selected study population. Review of supplement doses and calcium monitoring depends on individual risk; the evidence does not support universal avoidance.
What this answer covers
The trial studied vitamin D3 for three months in adults taking oral hydrochlorothiazide, excluding people with kidney disease, high calcium or calcium-metabolism disorders.
- Supplement or preparation
- Vitamin D
- Medication ingredient
- hydrochlorothiazide
Evidence and practical considerations
Side effects & toxicity
Exact hydrochlorothiazide labeling and/or human evidence supports the candidate with the stated route, duration, and risk boundaries.
- Exact scope
- vitamin D supplements with hydrochlorothiazide
- Medication form and route
- oral
- Timing or duration
- A 3-month trial evaluated up to 4,000 IU/day; case reports involved higher-risk or higher-dose exposures.
What remains uncertain
- Risk is conditional on dose, co-supplementation, renal function, and underlying calcium-metabolism disorders; no universal avoidance rule is supported.
Factors that may matter: vitamin D dose; calcium co-use; renal function; baseline calcium; hyperparathyroidism; granulomatous disease.
Read the supporting source summaries
Source 1: peer-reviewed human supplementation study
pmc.ncbi.nlm.nih.gov · Source check Jul 24, 2026
Population: Black adults taking hydrochlorothiazide in a randomized vitamin D dose-finding trial.
Vitamin D3 increased serum calcium, but hypercalcemia frequency was low in the studied population.
Selected population; people with renal disease, hypercalcemia, and calcium-metabolism disorders were excluded; limited duration.
Research assessment: · Open full citations ↗
Timing & monitoring
Exact hydrochlorothiazide labeling and/or human evidence supports the candidate with the stated route, duration, and risk boundaries.
- Exact scope
- vitamin D supplements with hydrochlorothiazide
- Medication form and route
- oral
- Timing or duration
- Disclosure is ongoing; calcium monitoring depends on dose and susceptibility.
What remains uncertain
- Risk is conditional on dose, co-supplementation, renal function, and underlying calcium-metabolism disorders; no universal avoidance rule is supported.
Factors that may matter: vitamin D dose; calcium co-use; renal function; baseline calcium; hyperparathyroidism.
Read the supporting source summaries
Source 1: peer-reviewed human supplementation study
pmc.ncbi.nlm.nih.gov · Source check Jul 24, 2026
Population: Black adults taking hydrochlorothiazide in a randomized vitamin D dose-finding trial.
Vitamin D3 increased serum calcium, but hypercalcemia frequency was low in the studied population.
Selected population; people with renal disease, hypercalcemia, and calcium-metabolism disorders were excluded; limited duration.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Research summary published |
Article revision: 3d666bef93a0d37c
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
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Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.