Short answer. In the United States, potassium iodide (KI) is sold without a prescription: "KI is available without a prescription" 1. The Nuclear Regulatory Commission supplies KI tablets free of charge to states that request them, for people inside the 10-mile emergency planning zone around commercial nuclear power plants 2. FDA doses range from 16 mg for newborns to 130 mg for adults, and KI should not be taken as a preventative before exposure 1.
Do I need a prescription for potassium iodide?
No. The FDA states that "KI is available without a prescription." 1 Buying it and taking it are two separate decisions: see below.
Who gets free KI tablets in the U.S.?
People living in the 10-mile emergency planning zone (EPZ) around a commercial nuclear power plant, if their state has asked for tablets 2. The NRC says: "The NRC supplies KI tablets, in accordance with FDA dosing guidelines, to States that request it." 2
NRC rules require states, including Tribal governments, with populations inside the EPZ to consider including KI in their emergency plans 2. Whether to adopt it, and how to distribute it, is left to state and local governments 12. To know whether tablets are available where you live, ask your state or local emergency management or health department.
What dose does the FDA recommend by age?
The FDA dose depends on age and on an exposure threshold, in centigray (cGy) 1.
| Group | Dose | Exposure threshold |
|---|---|---|
| Adults over 40 | 130 mg | > 500 cGy 1 |
| Adults over 18 through 40 | 130 mg | > 10 cGy 1 |
| Pregnant or lactating women | 130 mg | > 5 cGy 1 |
| Adolescents 12 through 18 | 65 mg (130 mg if over 150 lbs / 70 kg) | > 5 cGy 1 |
| Children over 3 through 12 | 65 mg | > 5 cGy 1 |
| Children over 1 month through 3 years | 32 mg (oral solution) | > 5 cGy 1 |
| Infants birth through 1 month | 16 mg (oral solution) | > 5 cGy 1 |
The thresholds are much lower for children and pregnant or lactating women than for adults over 40 1. The units are explained in our guide to sieverts, grays and millisieverts.
Should I take KI as a precaution?
No. The FDA warns that "KI should not be taken as a preventative before radiation exposure." 1 During an emergency, follow the instructions of state and local officials, given through the channels on our U.S. alerts page. Our general guide on potassium iodide compares guidance from several countries.
Frequently asked questions
Is KI available over the counter in the United States?
Yes. The FDA says KI is available without a prescription 1.
Does every U.S. state distribute KI?
No. The NRC supplies tablets to states that request them, for the 10-mile zone around commercial nuclear power plants 2. Adoption is at the discretion of state and local governments 1.
What is the adult dose of potassium iodide?
130 mg, according to the FDA table, for adults and for pregnant or lactating women; the exposure threshold that triggers it differs by age 1.
What dose is given to babies?
16 mg as an oral solution from birth through 1 month, and 32 mg from 1 month through 3 years 1.
Sources
- U.S. Food and Drug Administration — Frequently Asked Questions on Potassium Iodide (KI) — https://www.fda.gov/drugs/bioterrorism-and-drug-preparedness/frequently-asked-questions-potassium-iodide-ki (accessed 2026-10-20)
- U.S. Nuclear Regulatory Commission — Use of Potassium Iodide — https://www.nrc.gov/about-nrc/emerg-preparedness/about-emerg-preparedness/potassium-iodide-use (accessed 2026-10-20)
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Sources
- U.S. Food and Drug Administration · Frequently Asked Questions on Potassium Iodide (KI) checked 2026-10-20
- U.S. Nuclear Regulatory Commission · Use of Potassium Iodide checked 2026-10-20