What happens if I take too much Vitamin D ?
The European Food Safety Authority has stated that it is safe for anyone aged 11 or older to take 4,000IU (100micrograms) each day
They also state that a No Observed Adverse Effect Level (NOAEL) is 10,000IU (250micrograms) a day
( http://www.efsa.europa.eu/en/search/doc/2813.pdf )
They specifically include pregnant women, which implies that Vitamin D is very safe
Vitamin D is stored in your fat, rather than being water soluble, so your blood levels may depend on your size and weight
So a small person might choose to take 1-2,000IU (25-50micrograms) each day, while a large person might choose to take 5-10,000IU (250micrograms) each day
In 1999 the American Journal of Clinical Nutrition published a paper by Reinhold Veith with the title:
Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety
He reviews the whole subject of sunlight and vitamin D and cites many studies of the effects of vitamin D supplementation. He states:
“If there is published evidence of toxicity in adults from an intake of 250micrograms (10,000 IU) per day, and that is verified by the 25(OH)D concentration, then I have yet to find it.”
Dr John Cannell of the Vitamin D Council recently wrote to me about a personal experiment that he ran:
In 2012 I decided to do a toxicity study on myself to help answer a few questions.
I started taking 100,000 IU/day (2,500 micrograms) in June of 2012.
I measured my 25(OH)D and Urine CA/Cr ratio every week. The 25(OH)D was run by two different methods. Towards the end I also had a 1,25 and 24,25 run.
My 25(OH)D slowly increased to 300 ng/ml (750nmol/L) by LCMS at about 4 months. My serum and urine calcium and urine CA/CR ratio remained normal.
I wanted to see if sun exposure would affect 25(OH)D so I started sunbathing an hour every day for 2 weeks.
My 25(OH)D levels decreased to 250 ng/ml (625nmol/L) despite the fact I was still taking 100,000 IU/day.
It seemed to indicate that sun exposure will help reduce elevated 25(OH)D levels.
By six months my 25(OH)D level was 350 ng/ml (875nmol/L) but my serum CA, 24 hour urine calcium and CA/CR ratios remained normal.
However, I started having anorexia and nausea (some symptoms of D intoxication) when I got to 350 ng/ml (875nmol/L) so I stopped the vitamin D.
It took about 6 months for my 25(OH)D to get under 100 ng/ml (250nmol/L). The anorexia and nausea went away in about a month.
The different methods of measuring 25(OH)D showed about a 25% variance on some measurements. My 1,25 never went above normal but my 24,25 level was elevated the last 3 months.
It is assumed that toxicity is a side effect of hypercalcemia.
I guess the anorexia and nausea may have been psychosomatic as I got very nervous when my 25(OH)D got above 200 ng/ml (500nmol/L).
What I learn from this personal experiment is that it is very difficult to cause harm by taking too much Vitamin D