Radioactive Iodine Close Contact Restrictions

Treatment of Hyperthyroidism (assuming 50% uptake)^,*
Radiation dose	370 MBq (10 mCi)	555 MBq (15 mCi)	740 MBq (20 mCi)	1110 MBq (30 mCi)
Sleeping restriction (6 feet separation sleeping arrangement) for adults.	3 nights	6 nights	8 nights	11 nights
Sleeping restriction (6 feet separation of sleeping arrangement) for infants, children, and pregnant women.	15 nights	18 nights	20 nights	23 nights
Close contact restriction (6 feet separation) for children and pregnant women.	1 day	1 day	2 days	5 days

Treatment of Thyroid Cancer Remnant Ablation (assuming 2% uptake) (No thyroid)^,*
Radiation dose	1850 MBq (50 mCi)	3700 MBq (100 mCi)	5550 MBq (150 mCi)	7400 MBq (200 mCi)
Sleeping restriction (6 feet separation sleeping arrangement) for adults.	1 night	1 night	2 nights	4 nights
Sleeping restriction (6 feet separation of sleeping arrangement) for infants, children, and pregnant women.	6 nights	13 nights	18 nights	21 nights
Close contact restriction (6 feet separation) for children and pregnant women.	1 day	1 day	1 day	1 day

Adapted from American Thyroid Association Taskforce On Radioiodine Safety, Sisson JC, Freitas J, McDougall IR, Dauer LT, Hurley JR, Brierley JD, Edinboro CH, Rosenthal D, Thomas MJ, Wexler JA, Asamoah E, Avram AM, Milas M, Greenlee C. Radiation safety in the treatment of patients with thyroid diseases by radioiodine ¹³¹I: practice recommendations of the American Thyroid Association. Thyroid 2011 Apr;21(4):335-46.

^*IMPORTANT: The recommendations in the table above were derived by calculating the dose and time required to limit the effective dose to the infant below 1 mSv. Please be advised, these recommendations still permit a minimal amount of radiation transfer to the infant that is considered safe by the authorities. An average adult American is exposed to 6.2 mSv/year according to the Nuclear Regulatory Commission. The only way to totally avoid any radiation is to wait for all of it to decay (5-10 half-lives). Exposure of 1 mSv slightly increases the incidence of cancer to 1 in 10,000 people.

^**The half-life of 131I is around 8 days. To avoid all radiation exposure to the breastfed infant, close contact must be avoided for at least 5 half-lives, i.e. 40 days.