Tag: 400 iu

While the FDA has required companies to use metric units like milligrams (mg) and micrograms (mcg) on new supplement labels since 2020, many products still prominently feature **what is 400 IU equal to** alongside the updated measurements. This transition period creates confusion, as the IU value changes depending on the specific vitamin being measured.

An International Unit (IU) measures a substance's biological activity or potency, not its physical mass or volume. Therefore, determining what is 400 IU in mL is not a single, universal calculation, but one that is entirely dependent on the specific medication's concentration.