KI vs KIO₃: Why the FDA Approves Only Potassium Iodide

Potassium iodate (KIO₃) is sometimes marketed as an alternative to potassium iodide (KI) for radiation protection. The FDA has explicitly rejected it. Here's why.

Chemical Differences

• KI contains 77% iodine by weight; KIO₃ contains 59%
• KI is directly absorbed as iodide, the form the thyroid uses
• KIO₃ must be reduced to iodide in the body before it can work — adding a conversion step and delay

FDA's Position

In 1978, the FDA determined that KI is "substantially superior" to KIO₃ in safety, effectiveness, and speed of onset. The FDA has issued warning letters to sellers of KIO₃ products marketing them for radiation protection.

Why KIO₃ Exists

The WHO approves both KI and KIO₃ under different regulatory frameworks. Some tropical/developing countries prefer iodate because it's more stable in hot, humid environments. But in the US and most developed nations, KI is the standard.

How to Check What You're Buying

Always verify the active ingredient says "potassium iodide" (KI), not "potassium iodate" (KIO₃). Look for the chemical formula KI, not KIO₃. FDA-approved products (iOSAT, ThyroSafe) always contain KI.