The last I heard, the human body needs/consumes ~700 IU of Vitamin D per day. So I think your US levels are actually the full intake. One thing to consider is

The last I heard, the human body needs/consumes ~700 IU of Vitamin D per day. So I think your US levels are actually the full intake. One thing to consider is biological inefficiency. A 4,000 IU capsule contains 4,000 IUs, but that doesn't mean your body can't actually extract all 4,000 IUs. That said, I think 1k IUs is considered a standard dose for people without a deficiency. 4k IUs are generally used by people who are currently deficient, or have other issues that cause the deficiency. Doctors will sometimes prescribe doses up to 10k IUs for deficient people.