It's surely possible to take too much, but it's a lot. A typical over the counter tablet is 500-1500 IU of Vitamin D. Here[1]'s a study giving an oral dose of 100,000IU to a hundred people, and here[2]'s a paper suggesting muscular injections of 600,000IU in 10 people showed no evidence of metabolic abnormality. The Mayo Clinic[3] site says:
> Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity. This level is many times higher than the U.S. Recommended Dietary Allowance (RDA) for most adults of 600 IU of vitamin D a day.
That's 100x the recommended dose, every day, for months. Were you using powdered vitamin D instead of protein powder by mistake or something?
Deva Boone’s blog (an MD featured often on HN) describes a case where an extra 5000IU supplement caused neurological problems.
IIRC, there was no regard to other sources - e.g. she might have gotten 30,000 other IU per day from Milk and another amount from fish. Very unlikely - much more likely that something else made it toxic in that case.
Regardless, it is clear that the upper safe limit has significant variance and is not well characterized.
(Personally have been on 10,000IU daily for the past 7 years with no ill effects and possibly good effects, n=1 standard disclaimer)
How much a person can take without producing symptoms varies. My threshold was much lower than average probably because of chronic infections, e.g., Lyme disease.
Anyone taking substantial doses of vitamin D (>2000IU daily) should probably be getting regular blood tests to monitor their vitamin D levels. Vitamin D can accumulate in fat and the liver.
> Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity. This level is many times higher than the U.S. Recommended Dietary Allowance (RDA) for most adults of 600 IU of vitamin D a day.
That's 100x the recommended dose, every day, for months. Were you using powdered vitamin D instead of protein powder by mistake or something?
[1] https://pubmed.ncbi.nlm.nih.gov/28328526/ [2] https://pubmed.ncbi.nlm.nih.gov/28492140/ [3] https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...