Vitamin D Dosing

I recently wrote about my SWAMP hypothesis of curing a sinus (or upper respiratory) infection with Mucinex, salt and a large dose of vitamin D. In testing my hypothesis on my own infection, I may have overdosed a little on the vitamin D, so I've been doing some research on vitamin D dosing.

In several studies, subjects have been given a one-time dose of 100,000 IU of vitamin D. In one of those studies, the vitamin D levels were tested every few days and graphed. The vitamin D level peaked seven days after the dose, and the measured levels in the subjects didn't even come close to being toxic. (When you look at the graphs, keep in mind that the units are in nmol/L.) The maximum level in any subject was 48.1 ng/mL (ng/mL being the usual unit of measure for vitamin D levels).(1) This is a normal level of vitamin D.

In another study, subjects were given a one-time 100,000 IU dose:

A single dose in winter of 2.5 mg (100 000 IU) vitamin D has previously been shown to produce an elevation in 25-hydroxy vitamin D concentrations that lasts several months without any increase in serum calcium or other adverse side effects that occur only when such doses are given daily oven several months (29, 30); it is estimated equivalent to the decrease in amount of vitamin D made in the skin in winter compared with summer. Peak concentrations (about a threefold increase from baseline) occurred 2 weeks after ingestion of vitamin D (29).(2)

However, a letter to the British Medical Journal urges caution in taking a 100,000 IU dose:

We know from prior studies [eg 2] that some individuals will be harmed. Those with "a history of renal stones, sarcoidosis, or malignancy" were excluded from the cohort, presumably because they were thought to be at risk of harm.(3)

In a follow-up letter, the same letter writer mentioned undiagnosed vitamin D disregulation in people with "lesser immune dysfunction, such as Crohn's, Lupus or Rheumatoid Arthritis."(4) Further,

there are thousands, maybe hundreds of thousands, of folks for whom 100,000 IU of cholecalciferol [vitamin D3] would result in hospitalization or death.(5)

Vitamin D also interacts with some drugs. Here are the drugs with major, moderate and minor interactions with vitamin D3.(6)

For further reading, the Vitamin D Council has a page on vitamin D toxicity.

It looks like most people can safely take a 100,000 IU dose of vitamin D3, but there are people who should avoid it. Do some research and talk to your doctor if you think you might have a problem taking a large dose of vitamin D.

1. "Pharmacokinetics of a single, large dose of cholecalciferol1–3" by Marium Ilahi, Laura AG Armas, and Robert P Heaney. The American Journal of Clinical Nutrition, 2008;87:688 –91.
2. "Single-dose cholecalciferol suppresses the winter increase in parathyroid hormone concentrations in healthy older men and women: a randomized trial"  by Kay-Tee Khaw, Robert Scragg, and Sean Murphy. The American Journal of Clinical Nutrition, 1994;59-1040-4.
3. "A Therapy is Only Safe if it 'Does No Harm'" by Trevor G. Marshall, PhD, March 3, 2003, rapid response to "Effect of four monthly oral vitamin D3 (cholecalciferol) supplementation on fractures and mortality in men and women living in the community: randomised double blind controlled trial" in British Medical Journal, 2003;326:469.
4. "100,000 IU of Vitamin D is a Lethal Dose for Many in our Community" by Trevor G. Marshall, PhD, March 3, 2003, rapid response to "Effect of four monthly oral vitamin D3 (cholecalciferol) supplementation on fractures and mortality in men and women living in the community: randomised double blind controlled trial" in British Medical Journal, 2003;326:469.
5. Ibid.
6. Drugs.com Interaction Checker.