Vitamin D Deficiency in Adults: When to Test and How to Treat

Mayo Clinic Proceedings August 2010 vol. 85 no. 8 752-758
1. Kurt A. Kennel, MD,
2. Matthew T. Drake, MD, PhD, and
3. Daniel L. Hurley, MD
1. From the Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic, Rochester, MN
1. Individual reprints of this article are not available. Address correspondence to Daniel L. Hurley, MD, Division of Endocrinology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 hurley.daniel at mayo.edu

Recent evidence for the nonskeletal effects of vitamin D, coupled with recognition that vitamin D deficiency is common, has revived interest in this hormone. Vitamin D is produced by skin exposed to ultraviolet B radiation or obtained from dietary sources, including supplements.

Persons commonly at risk for vitamin D deficiency include those with inadequate sun exposure, limited oral intake, or impaired intestinal absorption. Vitamin D adequacy is best determined by measurement of the 25-hydroxyvitamin D concentration in the blood.

Average daily vitamin D intake in the population at large and current dietary reference intake values are often inadequate to maintain optimal vitamin D levels. Clinicians may recommend supplementation but be unsure how to choose the optimal dose and type of vitamin D and how to use testing to monitor therapy. This review outlines strategies to prevent, diagnose, and treat vitamin D deficiency in adults.
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PDF is attached at bottom of this page

Continuing Medical Education Questions from the end of the paper

CME Questions About Vitamin D Deficiency in Adults

1. Which one of the following patients is at greatest risk for vitamin D deficiency?

a. A formula-fed infant
b. A teenaged girl eating an unrestricted diet and taking a multivitamin
c. A 30-year-old male nursing home resident treated with phenytoin for epilepsy
d. A 70-year-old woman with osteopenia taking a calcium carbonate with vitamin D supplement
e. A 43-year-old male farmer

2. Which one of the following biochemical tests provides the best initial assessment of a person's vitamin D status?

a. Serum parathyroid hormone (PTH)
b. Serum 25-hydroxyvitamin D (calcidiol) [25(OH)D]
c. Serum 1,25-dihydroxyvitamin D (calcitriol) [1,25(OH)2D]
d. Serum bone alkaline phosphatase
e. 24-hour urine calcium excretion

3. Which one of the following sets of laboratory test findings (reference ranges provided parenthetically) is most suggestive of vitamin D toxicity?

• a. Serum calcium, 9.7 mg/dL (8.9-10.1 mg/dL); serum phosphorus, 4.0 mg/dL (2.5-4.5 mg/dL); 24-hour urine calcium, 250 mg/spec (25-300 mg/spec); 25(OH)D, 120 ng/mL (25-80 ng/mL); and PTH, 30 pg/mL (15-50 pg/mL)
• b. Serum calcium, 10.4 mg/dL (8.9-10.1 mg/dL); serum phosphorus, 4.8 mg/dL (2.5-4.5 mg/dL);
  24-hour urine calcium, 450 mg/spec (25-300 mg/spec); 25(OH)D, 120 ng/mL (25-80 ng/mL); and PTH, 20 pg/mL (15-50 pg/mL)
• c. Serum calcium, 11.0 mg/dL (8.9-10.1 mg/dL); serum phosphorus, 2.2 mg/dL (2.5-4.5 mg/dL); 1,25(OH)2D, 85 pg/mL (22-67 pg/mL); and PTH, 95 pg/mL (15-50 pg/mL)
• d. Serum calcium, 10.6 mg/dL (8.9-10.1 mg/dL); serum phosphorus, 4.0 mg/dL (2.5-4.5 mg/dL); 24-hour urine calcium, 450 mg/spec (25-300 mg/spec); 25(OH)D, 26 ng/mL (25-80 ng/mL); 1,25(OH)2D, 85 pg/mL (22-67 pg/mL); and PTH, 12 pg/mL (15-50 pg/mL)
• e. Serum calcium, 15 mg/dL (8.9-10.1 mg/dL); serum phosphorus, 4.0 mg/dL (2.5-4.5 mg/dL);
  24-hour urine calcium, 450 mg/spec (25-300 mg/spec); 25(OH)D, 35 ng/mL (25-80 ng/mL); 1,25(OH)2D, <10 pg/mL (22-67 pg/mL); and PTH, <6 pg/mL (15-50 pg/mL)

4. Which one of the following treatment strategies is most likely to be safe and effective to achieve optimal vitamin D levels in a person with little sun exposure?

a. Daily supplementation with 400 IU of vitamin D3 (D3) via a multivitamin
b. Daily supplementation with 800 to 1000 IU of vitamin
c. Daily supplementation with 50,000 IU of D3
d. Monthly supplementation with 50,000 IU of D2
e. One daily serving of fortified milk

5. Which one of the following statements about measuring 25(OH)D levels is correct?

• a. All patients should be tested for vitamin D deficiency before supplementation
• b. A patient with a 25(OH)D level of 10 ng/mL who is beginning treatment with 800 IU/d of D3 should be rechecked after 1 month
• c. A patient with a 25(OH)D level of 10 ng/mL who is beginning treatment with 50,000 IU of vitamin D 3 times weekly for 1 month
  to be followed by 50,000 IU once monthly should be rechecked after 1 month
• d. A patient with a 25(OH)D level of 10 ng/mL who is beginning treatment with 2000 IU/d of D3 should be rechecked after 6 months
• e. A patient with generous summertime sun exposure living at a high latitude with a low 25(OH)D level in spring should be supplemented and retested in the fall

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