Check the NIH vitamin D fact sheet before buying supplements
Added
The NIH Office of Dietary Supplements lists daily amounts by age and warns that too much vitamin D can be harmful, almost always from supplements. Upper limits count food, drinks, and supplements together, and a health care provider may advise higher doses to treat a deficiency.
The result
Result: NIH ODS: recommended intake is 15 mcg (600 IU) a day for most adults through age 70 and 20 mcg (800 IU) from age 71.
Note: Not medical advice. Talk to your doctor or pharmacist before starting any supplement, especially if you take medications.
Source
NIH Office of Dietary Supplements (opens the original source in a new tab). Check it for the latest numbers before you act.