Colecalciferol

Vitamins. Regulator of calcium-phosphorus metabolism

ATC code: A11CC05 (Colecalciferol (vitamin D3))

Brand names – drugs

Drisdol

Brand names – supplements

Solgar Vitamin D3, NOW Foods Vitamin D-3, Thorne Vitamin D

Supplements are not tested in clinical trials and are not registered as medications.

Mechanism of action

Colecalciferol (vitamin D3) is hydroxylated in the liver to 25-hydroxyvitamin D and then in the kidney to the active form 1,25-dihydroxyvitamin D (calcitriol). Calcitriol binds the nuclear vitamin D receptor and regulates intestinal calcium and phosphate absorption, renal calcium reabsorption, and bone mineralisation. It also modulates immune function, cell proliferation, and cytokine synthesis.

Indications

Postmenopausal osteoporosis

Adjunct

A required component of combination therapy for postmenopausal osteoporosis together with calcium and antiresorptive or anabolic agents (bisphosphonates, denosumab, teriparatide). USPSTF and meta-analyses show that combined calcium 1,000–1,200 mg and vitamin D 800–1,000 IU daily reduces hip fracture risk by 16% in at-risk populations. Vitamin D monotherapy in patients with normal bone density does not reduce fracture risk.

Vitamin D monotherapy is not indicated for fracture prevention in pre- or postmenopausal women without osteoporosis.

Sources

Rickets in children

First line

Cornerstone treatment and prevention of rickets in children. Prophylactic dose for term newborns is 400 IU daily from the first days of life, 800–1,000 IU daily for preterm infants. Therapeutic dose for established rickets is 2,000–5,000 IU daily for 30–45 days followed by prophylactic dosing. Efficacy is supported by decades of paediatric practice and is reflected in the AAP and Russian Paediatric Society guidelines.

In children with concomitant gastrointestinal disease (coeliac disease, cystic fibrosis, short bowel syndrome) doses are individualised with 25(OH)D monitoring.

Sources

Vitamin D deficiency

First line

First-line therapy for correcting vitamin D deficiency and insufficiency in adults. Standard loading regimens are 50,000 IU weekly for 8 weeks or 6,000 IU daily, followed by maintenance 1,500–2,000 IU daily. Target 25(OH)D is at least 30 ng/mL per the Endocrine Society and Russian clinical guidelines. Doses are 2–3 times higher in obesity, malabsorption syndromes, and in patients on anticonvulsants.

In chronic kidney disease colecalciferol is preferred over active metabolites (alfacalcidol, calcitriol) for initial therapy. In sarcoidosis and other granulomatous diseases, only with monitoring of serum calcium.

Sources

Falls prevention in older adults

Individual decision

In adults over 65 with confirmed vitamin D deficiency, 800–1,000 IU daily reduces the risk of falls in several meta-analyses. The 2018 USPSTF update found the effect insufficient in patients without deficiency and withdrew the prior recommendation. The decision is individualised based on 25(OH)D level, physical activity, and other fall risk factors.

Doses above 4,000 IU daily without clinical indications are not recommended – dedicated RCTs showed a paradoxical increase in fall risk.

Sources

Autoimmune disease prevention

Individual decision

The VITAL trial (BMJ 2022) showed a 22% reduction in autoimmune disease incidence in adults 50+ after 5 years of vitamin D 2,000 IU daily. The finding comes from a single cohort, has not been reproduced in other RCTs, and the effect accrues over years. International rheumatology societies do not recommend vitamin D as primary prevention of autoimmune disease.

Sources

NEJM: Vitamin D Supplements and Prevention of Autoimmune Disease (VITAL ancillary) (2022)

Prophylaxis of acute respiratory infections

Not recommended

The 2021 Cochrane review (46 RCTs, more than 75,000 participants) showed a modest effect on acute respiratory infections – about 2% absolute reduction, more pronounced in patients with baseline deficiency. WHO, NICE, and CDC do not include vitamin D in respiratory infection prophylaxis protocols. Routine prescribing in patients without deficiency is not justified.

Vaccination and hand hygiene remain the cornerstones of respiratory infection prevention.

Sources

Cochrane: Vitamin D supplementation for prevention of acute respiratory tract infections (2021)

Anti-aging and longevity (marketed indication)

Not recommended

The VITAL trial (NEJM 2019, more than 25,000 participants) did not show any reduction in cardiovascular or all-cause mortality from vitamin D 2,000 IU daily over 5 years. The 2014 Cochrane meta-analysis also found no effect on all-cause mortality in adults. International guidelines do not recommend vitamin D for slowing ageing or extending lifespan.

Sources

Practical notes

Timing and administration

Take with or immediately after a meal, preferably one containing fat – vitamin D is fat-soluble and absorption improves with dietary fat. Formulation matters: oil-based drops and capsules are absorbed better than aqueous emulsions in malabsorption syndromes. Time of day is not clinically important.

Monitoring

Check 25(OH)D 3 months after starting therapy. Target level 30–60 ng/mL (75–150 nmol/L). After the target is reached, retest annually. Levels above 100 ng/mL require dose reduction due to hypercalcaemia risk. Monitor serum calcium and creatinine during long-term high-dose therapy.

Food and drinks

Vitamin D interacts with several drug classes. Orlistat and cholestyramine reduce absorption – separate doses by at least 2 hours. Thiazide diuretics increase the risk of hypercalcaemia. Anticonvulsants (phenytoin, phenobarbital) accelerate vitamin D catabolism – the dose is doubled. Glucocorticoids reduce the effect – doses are adjusted by 25(OH)D level.

Special situations

In obesity (BMI above 30), effective doses are 2–3 times higher than standard because adipose tissue sequesters vitamin D. During pregnancy and lactation, prophylactic dose is 600–800 IU daily; in confirmed deficiency up to 4,000 IU daily with 25(OH)D monitoring. Infants receive prophylaxis from the first days of life regardless of feeding type.

Common myths

Myth: “all adults should take vitamin D continuously”. Fact: the recommendation applies to at-risk groups (northern latitudes, older adults, dark skin, anticonvulsants, obesity). Healthy people with normal 25(OH)D do not derive proven benefit.

Myth: “vitamin D treats everything from depression to cancer”. Fact: RCTs have not confirmed effects on cognition, depression, or cancer outcomes (VITAL, Cochrane). Only deficiency correction, rickets, and osteoporosis as adjunctive therapy are high-tier indications.

Myth: “D3 and D2 are equivalent”. Fact: D3 (colecalciferol) is more effective than D2 (ergocalciferol) per meta-analyses – it raises 25(OH)D faster and more stably.

Safety

Contraindications

Hypercalcaemia of any aetiology
Hypervitaminosis D
Calcium-based renal stones
Active pulmonary tuberculosis
Sarcoidosis and other granulomatous diseases (only with calcium monitoring)
Severe hypercalciuria

Serious adverse effects

Hypercalcaemia with uncontrolled high-dose use
Nephrocalcinosis and renal function decline with prolonged overdose

Common adverse effects

Dry mouth
Dyspepsia at high doses

Uncommon adverse effects

Hypercalciuria
Weakness and fatigue with overdose

PregnancyFDA A

FDA category A at recommended doses. Prophylactic use in pregnancy and lactation is encouraged. Doses above 4,000 IU daily without 25(OH)D monitoring are not recommended.

Breastfeeding

Transfers into breast milk in small amounts. On 400–600 IU daily in the mother, the infant receives less than 10% of daily needs – breastfeeding alone does not provide a prophylactic dose, so infants are supplemented directly.