Iodine
Supplements · Minerals · Supplement, Typed Supps
Your thyroid literally cannot make its hormones without it.
Stage by stage
- Intake (Tablet or kelp-based): Absorbed almost completely as iodide in the stomach and small intestine.
- Small intestine (Absorbed as iodide): Absorbed almost completely as iodide in the stomach and small intestine.
- Bloodstream (Taken up by thyroid): Actively taken up by the thyroid gland via a dedicated transporter.
- Thyroid (Builds thyroid hormone): Used to build thyroid hormones that regulate metabolism throughout the body.
What the evidence supports
- Preventing goitre and iodine-deficiency disorders — strong evidence. Salt iodisation is one of the most effective public health interventions of the last century.
- Preventing developmental impairment when deficient in pregnancy — strong evidence. Severe maternal deficiency causes irreversible cognitive impairment in the child. This is the reason iodine status in pregnancy is taken seriously.
- Improving thyroid function in people who are not deficient — insufficient evidence. Adding iodine when you already have enough can trigger thyroid dysfunction rather than improve it — in both directions.
Typical dose
150 mcg daily
Upper limit: 1,100 mcg daily for adults
Timing
Consistent daily intake matters more than timing.
Time to effect
- Weeks: Thyroid hormone levels reflect changes.
Medication interactions
- Thyroid medication (levothyroxine, carbimazole, methimazole): Iodine directly affects thyroid hormone production and can destabilise a dose that was working. (high)
- Lithium: Both suppress thyroid function; combined, the risk of hypothyroidism rises. (high)
- ACE inhibitors and potassium-sparing diuretics: Potassium iodide adds to potassium load. (moderate)
Common myth
“If a little iodine is good, more is better.” In reality: Both too little and too much iodine can disrupt thyroid function — a narrower window than most nutrients.
Food sources
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