Take a second look at vitamin D testing

The conversation about vitamin D testing and supplementation is heating up in the media and throughout medical journals these days. More patients are requesting a check of their vitamin D levels by their health care providers – oftentimes without any medical reason. The necessity of this costly test is the subject of ongoing debate in the community. The current cost for serum 25-hydroxyvitamin D measurement from Providence Lab Services is $86, plus a $24 phlebotomy fee.

We advise that you order vitamin D testing for only those patients who are at greatest risk for abnormal levels, such as individuals who have:

  • Rickets or osteomalacia
  • Fat malabsorption syndromes
  • Hyperparathyroidism
  • Osteoporosis
  • Renal or hepatic disease
  • Granulomatous disorders (i.e., sarcoidosis)

Testing also is indicated for patients who take certain medications on an ongoing basis, such as glucocorticoids, anticonvulsants and antiretroviral therapy.

Our recommendations are based on primary literature, published guidelines and consensus statements, as well as expert opinion.

Suggested dosing

Dietary Reference Intake (DRI)

The Institute of Medicine (IOM) updated DRI values for vitamin D in 2010. Assuming minimal sun exposure, the updated recommended dietary allowance values for vitamin D are:

  • 600 IU for males and females ages 1 to 70, including pregnant and lactating women
  • 800 IU for men and women older than age 70

Goals of treatment

Until a more defined consensus for vitamin D level is agreed upon, target a serum 25-hydroxyvitamin D level of at least greater than 20 ng/mL, and consider targeting greater than 30 ng/mL.

Initial therapy

  • 50,000 IU vitamin D2 (ergocalciferol) once weekly for approximately eight weeks (available as a prescription medication)
  • Vitamin D3 (cholecalciferol) 2,000 to 3,000 IU daily for approximately eight weeks (prescription not necessary)

Maintenance therapy

  • A commonly used maintenance regimen is 1,000 to 2,000 IU daily (sum of dietary intake plus vitamin D3 (cholecalciferol) if necessary; prescription not necessary)

*Note: Some variability may be noted in the vitamin D dosing and duration of therapy based on the pertinent medical condition(s) and 25-hydroxyvitamin D level.

Suggested monitoring

  • If a patient is taking 2,000 IU vitamin D2 (ergocalciferol) or D3 (cholecalciferol) per day or less, routine serum 25-hydroxyvitamin D monitoring is not required.
  • For vitamin D replacement therapy at a dose of greater than 2,000 IU per day, recommend monitoring the serum 25-hydroxyvitamin D level at baseline and again after three months of therapy.
    • Once a patient has taken a stable dose of vitamin D for at least three months and the serum 25-hydroxyvitamin D level has confirmed sufficient replacement, annual monitoring of 25-hydroxyvitamin D is indicated if the total daily dose exceeds 2,000 IU of vitamin D2 (ergocalciferol) or D3 (cholecalciferol).

Potential toxicity

  • Although not common, vitamin D toxicity is possible, and has been documented in the literature.
  • Clinically, vitamin D toxicity manifests as hypercalcemia that can range from asymptomatic elevated serum calcium labs requiring discontinuation of vitamin D supplementation, to more severe hypercalcemia requiring medical treatment.