Only take vitamin D if level is low

Dear Dr. Roach: These days, when vitamin D is recommended at every turn, I need to be sure I am taking the right dose. When I took 5,000 IU daily, my blood calcium levels increased and my doctor said to cut back to 2,000 IU daily. Now I read that we should be taking 5,000 IU daily because of COVID-19. Even my 23-year-old grandkids take this dose. Can vitamin D be harmful at these levels?

J.O.

Answer: During winter, most people north of the line between Atlanta and Los Angeles are unable to make adequate vitamin D, and low vitamin D levels are common.

However, large studies have failed to show much benefit in routine supplementation of vitamin D, and at this time should be used only for people with low vitamin D levels. People with risk factors for low vitamin D (those with darker skin, who are overweight, get little sun exposure, have osteoporosis or at risk for poor absorption of vitamin D) should be screened.

When vitamin D levels are low, then supplementation is appropriate. Most experts use 600-2,000 IU for treatment. Toxicity due to excess vitamin D is unusual at dosages at or below 8,000 IU daily. In my opinion, doses above 2,000 should be guided by measurement of blood levels.

A high calcium level is an indicator of excess vitamin D. However, the fact that you had high calcium at modest levels of vitamin D replacement makes me wonder if you also have a high level of parathyroid hormone. A high PTH level, usually from a benign tumor of the gland, is the most common cause of persistently high blood calcium levels.

Although some studies have found an association between low vitamin D levels and worse outcomes with COVID-19, vitamin D treatment of people with COVID-19 has so far not been shown to be helpful. Studies are ongoing.

In absence of good data, I would not recommend more than routine supplementation to treat or prevent vitamin D deficiency, but a dose of 600-1,000 IU daily is unlikely to be harmful and may possibly help.