A teaspoon of iodine is all a person requires in a lifetime, but because iodine cannot be stored for long periods by the body, tiny amounts are needed regularly.

Several international groups have made recommendations, which are fairly similar. IGN (formerly ICCIDD), WHO, and UNICEF recommend the following daily amounts:

age 0-5 years: 90 micrograms (mcg)/day; age 6-12 years: 120 mcg; older than 12 years: 150 mcg; pregnant and lactating women: 250 mcg.

A report by the Food and Nutrition Board, Institute of Medicine, National Academy of Sciences, USA, offers similar recommendations.

It calculates an "Estimated Average Requirement" (EAR) and from that derives a Recommended Daily Allowance (RDA). However, occasionally sufficient data are not available and instead an "Adequate Intake" (AI) is calculated, which may be set higher than the RDA would be, for safety. The recommendations for daily intake are as follows:

AI for infants:

age 0-6 months: 110 mcg/day; age 7-12 months: 130 mcg.

EAR's:

1-8 years: 65 mcg/day; 9-13 years: 73 mcg; 14 and older: 95 mcg.

RDA's:

1-8 years old: 90 mcg; 9-13 years: 120 mcg; 14 and older: 150 mcg; pregnancy: 220 mcg; lactation: 290 mcg.

The Food and Nutrition Board, Institute of Medicine also sets the tolerable upper limits of the daily iodine intake as 1.1 mg (1100 mcg) for adults, with proportionately lower levels for younger age groups.

Below are the tolerable upper intake level for iodine (micrograms per day) established by the Scientific Committee on Food, European Commission, and the U.S. Institute of Medicine.

References
Assessment of iodine deficiency disorders and monitoring their elimination. A guide for programme managers, 3rd edition. WHO/UNICEF/ICCIDD. Geneva, 2008.

Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. The U.S. Food and Nutrition Board, Institute of Medicine, National Academy of Sciences. Washington DC, 2000.