Description
Vitamin D3 (Cholecalciferol) is the natural form of vitamin D synthesized in the body from 7-dehydrocholesterol under skin UV-B radiation. The injectable depot form brings the vitamin directly into systemic circulation and bypasses the intestinal absorption variability of oral forms.
Per study reports Vitamin D3 is converted to 25-hydroxy-vitamin D in the liver and to 1,25-dihydroxy-vitamin D (Calcitriol, active form) in the kidney. Calcitriol acts via the vitamin D receptor in nearly all tissues and regulates calcium/phosphate homeostasis, immune function, cell proliferation, and gene expression in hundreds of pathways.
Vitamin D deficiency is a widespread research phenomenon, especially in northern latitudes and in populations with low sun exposure. Studies document associations with autoimmune diseases, cardiovascular mortality, and cancer risk.
The injectable form has very long action duration of 3-6 months per dose - a typical depot dose of 200,000-300,000 IU keeps the 25(OH)D level over months in the optimal range (30-50 ng/ml).
Pharmacokinetically 25(OH)D has a half-life of 2-3 weeks, the active Calcitriol of a few hours. The depot vitamin D3 injection bypasses the oral absorption variability that makes dosing difficult in research setups.
Known effects with correct dosing are very mild: with overdosing hypercalcemia and associated effects (nephrocalcinosis, soft tissue calcifications). Blood test control (25(OH)D) every 3-6 months recommended.
You can order Vitamin D3 as an oily injection solution in 10-pack at 10ml with 20000 IU per ml.
This information is for research and educational purposes only. No medical recommendations.
Risks & Safety
Vitamin D3 is considered well tolerated per study reports at correct dosing. As a fat-soluble vitamin in injectable depot form, however, the central risk point is accumulation, since the body does not simply excrete an excess renally.
Observed in studies and user reports:
- Hypervitaminosis risk: with overdosing the literature documents hypercalcemia, with downstream effects such as nephrocalcinosis and soft tissue calcifications. The long depot action of 3-6 months makes an overdose difficult to correct.
- Injection site: as an oily intramuscular solution, mild redness, pressure or transient irritation at the injection site is documented.
- Cofactor dependence: the literature describes that magnesium and K2 status influence vitamin D utilization and that an imbalance can shift calcium distribution.
- Long-term data: the mechanism is well characterized, yet specific data on very long-term high-dose depot use in research settings remain limited.
Monitoring via bloodwork is recommended. This classification does not replace medical advice. Risk and responsibility for any actual use lie entirely with the buyer.
Studies
- Vitamin D Deficiency - New England Journal of Medicine 2007, Holick: pivotal review of vitamin D deficiency, skeletal and non-skeletal effects, prevention and treatment.
- Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease - NEJM 2019, Manson et al (VITAL trial): 25,871 participants, no significant effect on primary cardiovascular or cancer endpoints, suggestive reduction in cancer mortality.
- Vitamin D Supplementation and Prevention of Type 2 Diabetes - NEJM 2019, Pittas et al (D2d trial): diabetes prevention study in high-risk adults.
- Supplemental Vitamin D and Incident Fractures in Midlife and Older Adults - NEJM 2022, LeBoff et al (VITAL fracture sub-study): no significant effect on fractures in a population not selected for deficiency.
- Vitamin D Deficiency and Risk of Cardiovascular Disease - Circulation 2008, Wang et al: prospective Framingham Offspring study on the association between 25(OH)D level and cardiovascular events.