B tier · viable
Repletion of genuine vitamin D deficiency is well established and depot injection raises 25(OH)D comparably to oral dosing in small trials, but the comparative evidence is thin, the injectable is not approved in every major market, and repeated high-dose injections have produced a documented series of severe hypercalcaemic toxicity.
injectable vitamin d3
Injectable cholecalciferol is a depot formulation used in some countries to correct vitamin D deficiency where adherence to oral dosing is unreliable. It raises 25-hydroxyvitamin D effectively, but the small comparative trials show little advantage over oral repletion and the depot route removes the ability to stop quickly if levels overshoot.
the explanation
This is a long-acting vitamin D shot used in some countries to fix a genuine deficiency. It works, but studies suggest tablets work about as well, and repeated large injections have caused serious calcium overload in documented cases.
regulatory status
Licensed in some markets; not FDA-approved as an injectable
Injectable cholecalciferol ampoules are marketed in a number of countries including France and India, and are used clinically in Europe; no FDA-approved injectable cholecalciferol product was identified for the US, where approved parenteral vitamin D drugs are the activated analogues used in renal disease rather than cholecalciferol itself. Oral cholecalciferol is regulated as a dietary supplement in the US.
how it works · proposed mechanism
Cholecalciferol is a prohormone requiring two sequential hydroxylations before it acts on a nuclear receptor.
Two-step hydroxylation to calcitriol
Hepatic CYP2R1 converts cholecalciferol to 25(OH)D, the circulating storage form measured clinically, and renal CYP27B1 converts that to 1,25(OH)2D. Only the final metabolite has meaningful vitamin D receptor affinity.
VDR-mediated calcium absorption
Calcitriol binds the nuclear vitamin D receptor, which heterodimerises with RXR and upregulates intestinal calcium and phosphate transport plus osteoclastic bone remodelling. Tight feedback through PTH and FGF23 normally caps calcitriol production.
Depot kinetics and toxicity
Intramuscular cholecalciferol distributes into adipose and muscle lipid, releasing slowly over months rather than days. That same reservoir is why toxicity from repeated injection resolves over many months rather than on discontinuation.
what’s reported
evidence shape
5 sourcesThe composition of the cited literature by study type. This describes the shape of the evidence, not its quality — and it does not by itself set the grade.
⚠ the catch
The depot advantage — one administration lasting months — is also the safety problem, because there is no way to withdraw the dose once given. The largest published injection-associated toxicity series found a median seven months, and up to eighteen, before hypercalcaemia resolved.
key published findings
- Human trial: PLOS ONE (2017) randomised placebo-controlled pilot of a single 100,000 IU intramuscular cholecalciferol injection (n=18; 12 active, 6 placebo) raised 25(OH)D to 70.9 nmol/L at day 28 versus 32.7 nmol/L on placebo, comparable to an escalating oral regimen in a parallel open-label cohort (n=43; 83.4 vs 42.5 nmol/L), with the injected form peaking at four weeks and sustained across three months.
- Human case series: prospective study of 32 vitamin D toxicity patients in Kashmir, all attributed to repeated 600,000 IU intramuscular cholecalciferol injections, median cumulative dose 4,200,000 IU (range 1.8-30 million), median 25(OH)D 306 ng/mL (range 105-2,800) and median serum calcium 13.95 mg/dL (Indian J Endocrinol Metab, 2019).
- Human case series (clinical burden): in that same cohort, gastrointestinal symptoms occurred in 93.7%, azotaemia in 78.1%, polyuria/polydipsia in 46.8%, altered mental status in 37.5%, nephrocalcinosis in 18.7% and pancreatitis in 12.5%, with hypercalcaemia taking a median 7 months (range 4-18) to resolve.
- Review: a 2018 Nutrients review of 13 published vitamin D toxicity case reports found 25(OH)D concentrations of 150-1,220 ng/mL and serum calcium of 11.1-23.1 mg/dL, with causes spanning manufacturing errors, patient misuse and physician over-prescribing, and routes including intramuscular injection.
- Human trial: an Indian Journal of Endocrinology and Metabolism (2017) randomised comparison of oral versus intramuscular vitamin D replacement in apparently healthy vitamin D deficient adults reported both routes to be effective at raising 25(OH)D, supporting oral repletion as the default where adherence is not a barrier.
limitations of the evidence
- The randomised comparative data are small — the best-characterised IM arm comprised 12 active participants — and endpoints are biochemical 25(OH)D rather than fractures, falls or other clinical outcomes.
- Injectable cholecalciferol products differ substantially in strength between markets, so pharmacokinetic findings from one ampoule strength do not generalise across countries.
- Most reported toxicity comes from settings where very high-strength injections were used repeatedly outside guideline recommendations, which limits how directly those harms apply to licensed single-administration use.
documented safety signals
- Hypercalcaemia with nephrocalcinosis, acute kidney injury and pancreatitis documented in a 32-patient prospective series of injection-associated vitamin D toxicity.
- Prolonged toxicity duration owing to depot storage, with a median 7 months and up to 18 months to resolution of hypercalcaemia.
- Hypervitaminosis D with acute interstitial nephritis has been reported in association with vitamin D injections.
- Contraindicated in hypercalcaemia, hypercalciuria, and generally in granulomatous disease and some lymphomas where extrarenal 1-alpha-hydroxylase activity is unregulated.
- Interaction risk with thiazide diuretics and calcium supplementation, both of which raise serum calcium.
identity
| full name | Injectable cholecalciferol (vitamin D3) |
| category | Nutritional |
| modality | small molecule |
| formula | C27H44O |
| molar mass | 384.6 g/mol |
| cas | 67-97-0 |
laboratory handling
| storage | Cholecalciferol ampoules are stored at controlled room temperature protected from light; the molecule is oxygen- and light-sensitive and isomerises on heating, so ampoules are amber or cartoned and are not refrigerated. |
| solubility | Cholecalciferol is a lipophilic secosteroid, practically insoluble in water and freely soluble in ethanol and vegetable oils; injectable presentations are oily or alcoholic solutions rather than aqueous, which is what gives the intramuscular depot its slow-release behaviour. |
| co-studied with | Vitamin D status interacts directly with calcium intake, magnesium status and vitamin K2-dependent carboxylation of osteocalcin and matrix Gla protein; the toxicity literature consistently shows that concurrent calcium supplementation raises hypercalcaemia risk during vitamin D repletion. |
Handling information describes laboratory practice for a research reagent. It is not a preparation guide for use in humans.
the receipts
5 citedPLOS ONE · 2017 · randomized
Indian Journal of Endocrinology and Metabolism · 2019 · observational
Nutrients · 2018 · reviews
Indian Journal of Endocrinology and Metabolism · 2017 · randomized
Maturitas · 2012 · observational
others in Nutritional