The best reason to take vitamin D is when level is low

Dear Dr. Roach: When vitamin D is recommended, 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. Can vitamin D be harmful? — J.O.

Dear J.O.: During winter, most people north are unable to make adequate vitamin D, and low levels are common. However, studies have failed to show much benefit in supplementation of vitamin D, and should be used only for people with low vitamin D levels. People with risk factors for low vitamin D should be screened.

When levels are low, 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. 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 is the most common cause of persistently high blood calcium levels. I would recommend you ask your doctor about checking your parathyroid hormone level.

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.