Tag: Vitamin conversion

About half of all US adults take dietary supplements [1.9.1]. A common point of confusion on labels is dosage units: **is 1000 IU the same as 1000 mg?** The answer is a definitive no, and understanding why is critical for your health and safety.

In pharmacology, International Units (IU) are used for fat-soluble vitamins like A, D, and E, as well as for hormones, vaccines, and some medications [1.5.1, 1.5.3]. So, which one is bigger, IU or mg? The answer is that they measure entirely different things and cannot be directly compared.

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.