I've been doing just fine with 2,000 IU of Vitamin D - have taken it daily for 20 years. I also get lots of sunshine and eat plenty of eggs and fatty fish.
There are people who always have to overdo a good thing. I know people who spend a couple hundred dollars a month on all sorts of vitamins and gimmicky supplements.
If you eat well and get some exercise, all you really need for supplements is Vitamin D, C and Zinc.
I’ve been doing just fine with 2,000 IU of Vitamin D - have taken it daily for 20 years.
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I bet your body deactivates a lot of the vitamin d you take. Having taking it for so long, I bet you have stored enough to not need to take it for years.