Vitamin D treatment regimens

Evidence to support a specific target serum 25-hydroxyvitamin D concentration to improve outcomes is lacking. A reasonable target of vitamin D supplementation is a serum 25-hydroxyvitamin D concentration of 50 nanomol/L or more.

Vitamin D absorption is affected by many factors (eg weight, medical conditions, drugs) so the dose required to meet this target varies, even between patients with similar baseline serum 25-hydroxyvitamin D concentration.

For patients with vitamin D deficiency complicated by osteomalacia or rickets, see Osteomalacia and rickets.

For children with vitamin D deficiency, use the same colecalciferol doses as those used for Rickets caused by vitamin D deficiency.

For adults with uncomplicated mild vitamin D deficiency, consider lifestyle measures to increase exposure to sunlight first line. If supplementation is preferred, use:

1 colecalciferol 25 to 50 micrograms (1000 to 2000 international units) orally, daily vitamin D deficiency, mild    

OR

1 colecalciferol 175 to 350 micrograms (7000 to 14 000 international units) orally, weekly.    

To treat uncomplicated moderate to severe vitamin D deficiency, higher doses are used, although long-term safety data for these doses is not available. A suitable regimen is:

colecalciferol 75 to 125 micrograms (3000 to 5000 international units) orally, daily for 6 to 12 weeks, followed by 25 to 50 micrograms (1000 to 2000 international units) orally, daily. vitamin D deficiency, moderate to severe    

Consider using a higher dose in obese patients, and patients taking a drug that alters metabolism and storage of 25-hydroxyvitamin D in the liver (eg rifampicin or some antiepileptics). Very high doses (eg 1250 micrograms [50 000 international units] weekly) are sometimes used to treat patients with known fat malabsorption disorders (eg due to cystic fibrosis, coeliac disease or inflammatory bowel disease) or gastrectomy, or severe symptomatic deficiency, although safety data for these doses is not available.

Higher doses taken less frequently (eg taking the total monthly dose once a month) can be considered to improve adherence. These regimens may increase the risk of dosing errors, so are not routinely recommended first line. Megadose therapy with 7500 to 12 500 micrograms (300 000 to 500 000 international units) is occasionally used for patients with severe deficiency and poor adherence; however, safety data are limited and it is associated with an increased risk of falls in older people.

Measure the serum 25-hydroxyvitamin D concentration after 6 months in patients with baseline mild deficiency, and 3 months in patients with baseline moderate to severe deficiency. Earlier testing can be considered in patients with particularly severe deficiency or persistent symptoms, and those with fat malabsorption or gastrectomy. After reaching the target serum 25-hydroxyvitamin D concentration, no further testing is needed unless risk factors change. Most patients need ongoing low-dose (ie colecalciferol 25 to 50 micrograms [1000 to 2000 international units]) treatment.

The formulations of colecalciferol available in Australia are unlikely to cause vitamin D toxicity. However, if toxicity from colecalciferol occurs, see Hypercalcaemia caused by vitamin D toxicity.