Determining median urinary iodine concentration that indicates adequate iodine intake at population level

Bull World Health Organ. 2002;80(8):633-6.


Objective: Urinary iodine concentration is the prime indicator of nutritional iodine status and is used to evaluate population-based iodine supplementation. In 1994, WHO, UNICEF and ICCIDD recommended median urinary iodine concentrations for populations of 100- 200 micro g/l, assuming the 100 micro g/l threshold would limit concentrations <50 micro g/l to </=20% of people. Some scientists felt this proportion was unacceptably high and wanted to increase the threshold above 100 micro g/l. The study was carried out to determine the frequency distribution of urinary iodine in iodine-replete populations (schoolchildren and adults) and the proportion of concentrations <50 micro g/l.

Method: A questionnaire on frequency distribution of urinary iodine in iodine-replete populations was circulated to 29 scientific groups.

Findings: Nineteen groups reported data from 48 populations with median urinary iodine concentrations >100 micro g/l. The total population was 55 892, including 35 661 (64%) schoolchildren. Median urinary iodine concentrations were 111-540 (median 201) micro g/l for all populations, 100-199 micro g/l in 23 (48%) populations and >/=200 micro g/l in 25 (52%). The frequencies of values <50 micro g/l were 0-20.8 (mean 4.8%) overall and 7.2% and 2.5% in populations with medians of 100-199 micro g/l and >200 micro g/l, respectively. The frequency reached 20% only in two places where iodine had been supplemented for <2 years.

Conclusion: The frequency of urinary iodine concentrations <50 micro g/l in populations with median urinary iodine concentrations >/=100 micro g/l has been overestimated. The threshold of 100 micro g/l does not need to be increased. In populations, median urinary iodine concentrations of 100-200 micro g/l indicate adequate iodine intake and optimal iodine nutrition.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Child
  • Deficiency Diseases / epidemiology
  • Deficiency Diseases / urine*
  • Female
  • Global Health
  • Humans
  • Iodine / administration & dosage
  • Iodine / deficiency
  • Iodine / urine*
  • Male
  • Nutritional Status*
  • Population Surveillance*
  • Reference Values
  • Surveys and Questionnaires


  • Iodine