[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Vitamins](https://durgical.com/en/pharmacology/classes/vitamins/) › Ergocalciferol # Ergocalciferol ## Vitamins? Vitamins Vitamin D2, made from plants and fungi. Activated like D3; prescribed for hypoparathyroidism and hard-to-treat rickets. Its safety margin is narrow. Updated Nov 1, 2026 Also called: vitamin D2 ## Quick facts **Group** [Vitamins](https://durgical.com/en/pharmacology/classes/vitamins/) **Target** Vitamin D receptor (VDR), through its active metabolite **Used for** Hypoparathyroidism · Refractory **Key effects** Mostly signs of excess · Thirst **Monitor** Blood calcium · Kidney function and phosphate **ATC** A11CC01 No doses: the clinician sets them by the current guideline. On this page - The basics Mechanism of action - Indications - Adverse effects - Pharmacokinetics - Memory aid - Safety Contraindications - Key interactions - What is monitored - Administration and safety - Pregnancy and breastfeeding - Nursing care - Study Test yourself - Connections Connections ## Mechanism of action Ergocalciferol is converted in the liver to 25-hydroxyvitamin D and in the kidney to the 1,25-dihydroxy form. The active metabolite increases absorption of calcium and phosphate in the gut, mobilises them from bone and increases their reabsorption in the kidney tubule, a step regulated by parathyroid hormone. - Liver: ergocalciferol → 25-hydroxyvitamin D - Kidney: → 1,25-dihydroxyvitamin D (active) - Gut, bone and kidney release more calcium and phosphate into blood ## Indications - Hypoparathyroidism [Hypoparathyroidism (incl. post-thyroidectomy hypocalcaemia) →](https://durgical.com/en/conditions/hypoparathyroidism/) - Refractory (vitamin D-resistant) rickets [Rickets and osteomalacia →](https://durgical.com/en/conditions/rickets-and-osteomalacia/) - Familial hypophosphataemia ## Adverse effects ### Common - Mostly signs of excess: loss of appetite, nausea, weakness, weight loss, vague aches, constipation - Thirst, frequent urination and night-time urination ### Serious (rare, important) - High blood calcium (hypercalcaemia): weakness, nausea, vomiting, constipation, thirst, frequent urination, confusion - Kidney stones and kidney damage - Calcium deposits in the heart, blood vessels and lungs - Nephrocalcinosis and possibly irreversible kidney failure - Slowed growth in children ## Contraindications - Hypercalcaemia - Malabsorption syndrome - Hypervitaminosis D or abnormal sensitivity to vitamin D ## Key interactions **Mineral oil** Reduces absorption of vitamin D **Thiazide diuretics** Can cause hypercalcaemia in hypoparathyroid patients taking ergocalciferol **Other vitamin D or calcium supplements** Add to the total intake and to the risk of toxicity ## What is monitored - Blood calcium, frequently when high doses are used - Kidney function and phosphate - In breastfed infants of treated mothers: the infant's calcium ## Administration and safety - Total vitamin D from fortified foods, supplements and other prescriptions is reviewed before starting. - Calcium and phosphate intake are managed alongside it; a low-phosphate diet may be needed. ## Pregnancy and breastfeeding Amounts above the recommended intake are avoided unless clearly needed: excess vitamin D caused fetal abnormalities in animals. Its active metabolite passes into milk and can raise the infant's calcium. ## Nursing care - Teach the signs of hypercalcaemia: thirst, frequent urination, nausea, constipation, weakness, confusion. - Remind that lab tests are done before and during treatment. - Ask about kidney or liver disease and malabsorption. ## Pharmacokinetics **Absorption** Fat-soluble; absorbed from the gut, possibly less in older adults; mineral oil reduces absorption **Metabolism** Activated by the liver and then the kidney **Onset and duration** Delayed by about 10–24 hours while active metabolites are made; toxicity can last two months or more after stopping ## Memory aid D2 from plants, D3 from skin: both take the same «liver then kidney» road; ERGO, watch the calcium. ## Test yourself Think of the answer, then tap the question to see it. ## What are the three label indications of prescription ergocalciferol? Hypoparathyroidism, refractory rickets and familial hypophosphataemia. ## Why can vitamin D toxicity last for weeks after stopping ergocalciferol? It is fat-soluble and stored, so effects can persist for two months or more. ## Which diuretic class can push a patient on vitamin D into hypercalcaemia? Thiazide diuretics. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/ergocalciferol/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) ## Connections ## Related drugs 2 - [Colecalciferol](https://durgical.com/en/pharmacology/colecalciferol/) - [Calcitriol](https://durgical.com/en/pharmacology/calcitriol/) ## Related conditions 2 - [Hypoparathyroidism (incl. post-thyroidectomy hypocalcaemia)](https://durgical.com/en/conditions/hypoparathyroidism/) - [Rickets and osteomalacia](https://durgical.com/en/conditions/rickets-and-osteomalacia/) [← Back to the class: Vitamins](https://durgical.com/en/pharmacology/classes/vitamins/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - ERGOCALCIFEROL capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=87e80b1f-e376-45ba-825b-a6fda4b82325) (DailyMed (U.S. National Library of Medicine), 2026); [Ergocalciferol: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a616042.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=A11CC01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/ergocalciferol/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/ergocalciferol/