New questions raised on the safety of long-term supplementation at a popular upper limit dose
High-dose advocates have been drawing the safety line at 10,000 IU of supplementation for vitamin D. In 2011 even the Endocrine Society “approved” this limit. In 2020, however, a case report from New York challenged it.
“We present a case of Vitamin D Toxicity (VDT) in a patient,” wrote Neha Sharma et al, “following self-medication with mega doses that far exceeded the prescribed dosage. He presented to us with Acute Kidney Injury (AKI) and elevated serum 25(OH)-vitamin D levels.”
The patient, a 73-year-old man, for five days had suffered “lower extremity pain, increased shortness of breath and insomnia.” His medical history included heart issues and he had stage-III chronic kidney disease.
He was on more than a few medications plus various supplements including “5000 IU vitamin
D twice daily for a total daily dose of 10,000 IU per day, for many years.”
Doctors found his vitamin D level over 100 and his calcium 12.8 (normal: 8.6-10.2). They said he had “acute-on-chronic kidney injury.” They indicate his doctor should have advised him not to take such a large dose because of his kidney problem.
In 2021, somebody on reddit said, “You can’t overdose on vitamin D by taking 10,000 IU a day.” Then they said, “The IOM and the Endocrine Society recognize that up to 10,000 IU/d is completely safe in healthy adults for up to 5 months.”
The IOM’s current limit is 4000 IU, not 10,000. The Endocrine Society’s 10,000 IU limit is not time-restricted. Its advice was laid out here:
We suggest that the maintenance tolerable upper limits (UL) of vitamin D, which is not to be exceeded without medical supervision, should be… 4000 IU/d for everyone over 8 yr. However, higher levels of… 10,000 IU/d for children and adults 19 yr and older may be needed to correct vitamin D deficiency.
This guideline is linked from the ES page on vitamin D. There is no indication the ES put a term limit on their 10,000 limit. To be fair, the Society guideline suggested the public could take up to 4000 IU daily without the supervision of a doctor, but that doctors could safely prescribe up to 10,000 IU per day. (Basically the 4000 is for maintenance and the 10,000 for correction.)
The case report seems to indicate the patient went to 10,000 on his own without medical supervision, i.e., violated their guideline. Moreover, the guideline is for people at risk of deficiency and the patient was not. Presumably no doctor would have prescribed 10,000 firstly because they would have known his vitamin D level was already high and, secondly, because he had poor kidney health.
10,000 IU should not be considered a safe daily dose for years or indefinitely for people with kidney problems. The report did not say why the man was taking so much, whether it was prescribed to him, or if it was entirely his idea.
Sharma, N., Landsberg, E., Kumar, V., & Gambhir, H. (2020). A Curious Case of Hypervitaminosis D. Cureus, 12(6), e8515. https://doi.org/10.7759/cureus.8515