Iodine deficiency is an insufficient intake of iodine from food. Iodine is an essential component of thyroid hormones: without it, thyroxine (T4) and triiodothyronine (T3) cannot be synthesized.
Iodine deficiency remains the leading preventable cause of brain-development disorders in the world. Iodine sufficiency is assessed by the median urinary iodine concentration in a population.
Why iodine is needed
The thyroid gland captures iodine from the blood and builds it into hormone molecules that govern metabolism, growth and the development of the nervous system. When iodine is lacking, the gland enlarges in an attempt to capture more — this is how a goiter forms.
Why deficiency is dangerous
Chronic deficiency leads to goiter and hypothyroidism. Deficiency is especially dangerous in pregnancy: iodine is critical for the development of the fetal brain. Severe deficiency causes cretinism — irreversible mental and physical retardation, while a milder one is linked to reduced cognitive function in children.
Prevention
The main method is iodized salt. Rich in iodine are sea fish and seafood, seaweed, dairy products and eggs. Pregnant and breastfeeding women have a higher requirement and are often advised to take extra iodine as prescribed by a doctor. An excess of iodine is also harmful, so it is important not to exceed reasonable doses.
Reference ranges
Intake norms (RDA) and WHO criteria for the population median urinary iodine:
| Adults (RDA) | 150 µg/day |
| Pregnant / breastfeeding | 220 / 290 µg/day |
| Median urinary iodine: deficiency | <100 µg/L (severe <20) |
| Median urinary iodine: normal | 100–199 µg/L |
Calculate using this marker
Calculators where Iodine deficiency is used directly:
Frequently asked questions
Does everyone need to take iodine pills?
For most people, iodized salt and an ordinary diet are enough. Taking extra iodine supplements is justified mainly in pregnancy and breastfeeding and is prescribed by a doctor — uncontrolled high doses are harmful to the gland.
How can you tell if you lack iodine?
It is hard to determine this from a blood test in an individual. Iodine sufficiency is assessed by urinary iodine at the population level; indirect signs of deficiency are an enlarged gland (goiter) and signs of hypothyroidism.