Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston
PHILADELPHIA -- There were no toxic levels of calcium in patients taking high-doses of vitamin D, a small retrospective study showed.
A total of 121 patients without kidney or liver dysfunction taking high-dose vitamin D (2,000 to 7,000 IU/day) also had their calcium blood levels assessed over 4 years, according to Neena E. Thomas-Eapen, MD, of the University of North Dakota Center for Family Medicine in Minot, N.D., and colleagues.
None of these patients had hypercalcemia, defined as a calcium level greater than 10.5 mg/dL, Thomas-Eapen reported here at the annual meeting of the American Academy of Family Physicians.
"We want physicians to know that if there is a need for vitamin D supplementation, which is very important for bones, the brain, the endocrine and the immunological systems, they should feel free to use a few thousand international units to 7,000 international units of vitamin D safely in patients with normal liver and kidney functions," Thomas-Eapen told MedPage Today.
"I mostly use a standard of 2,000 international units daily, but sometimes between 2,000 to 7,000 international units," she said.
"I had not seen hypercalcemia in practice in patients with higher doses of vitamin D, but I wanted to conduct this study to quantify the data," she said.
The literature says that higher doses of vitamin D cause hypercalcemia. And the Institute of Medicine in 2010 recommended maximum vitamin D levels of between 1,000 to 4,000 IU per day.
"But in practice, I have seen that sometimes we need a higher dosage to bring up those levels, particularly in patients with osteoporosis or osteopenia," she said.
Thomas-Eapen and colleagues retrospectively reviewed patient charts and found 121 with both vitamin D and calcium levels recorded between 2008 and 2011.
Patients ranged in age from 30 to 90 and all patients had a minimum calcium intake of about 1,000 mg daily from all sources.
Vitamin D dosage ranged from 800 to 7,000 IU daily. As the level of vitamin D increased, so did the level of calcium, but it never breached the 9.5 mg/dL mark.
For the year 2008, the mean level of calcium for vitamin D levels of less than 1,000 IU was 9.1 mg/dL. That rose to 9.2 for vitamin D levels between 1,001 and 2,000 IU and 9.4 for vitamin D levels between 2,001 and 3,000 IU. But when vitamin D levels were 3,000 and above, the calcium levels remained at 9.5. These figures remained steady for each year of the study.
Thomas-Eapen said that she had previously reported that none of these patients developed kidney stones.
"On a practical basis, physicians should feel comfortable using a higher dose of vitamin D as the clinical situation indicates, but they should also check vitamin D and calcium levels in the winter," she concluded.
The study was limited by its retrospective nature and small size, Thomas-Eapen said. She added that a multicenter study with a larger sample size and longer duration would be useful to confirm these results.
Thomas-Eapen reported she has no conflicts of interest.
Primary source: American Academy of Family Physicians