Comparison guide

Which iodine supplement should you take?

Adult iodine needs are small, 150 mcg/day, and in fortified countries iodised salt and food cover most people. The forms differ mainly in dose control: some deliver a predictable microgram dose, others an unpredictable or milligram-scale one. With iodine, too much causes thyroid disease just as too little does.

The options, compared

Option	Evidence	Best for	The honest note
Iodine	Moderate evidence	Pregnancy and low-intake diets	A standard supplement meets the adult RDA of 150 mcg/day; check whether your salt is iodised before assuming a gap. In mild deficiency, the largest pregnancy trial found no IQ benefit for children.	View
Potassium Iodide	Moderate evidence	Dose-controlled everyday supplement	The salt in most prenatal and standard supplements, usually at 150 µg. The 130 mg tablet is an emergency thyroid-blocking dose, to take only when public health authorities instruct.	View
Kelp (Iodine Source)	Limited evidence	Not recommended	Iodine content varies more than 100-fold and labels are often inaccurate, and in a trial it raised TSH in people who were not deficient. It can also carry arsenic, cadmium and lead.	View
Lugol's Iodine Solution	Limited evidence	Clinician-directed use only	Lugol's 5% supplies roughly 6 mg of iodine per drop, many times the adult upper limit of about 1,100 µg/day. Self-dosing is a well-documented way to trigger thyroid dysfunction.	View

Our verdict

If you need iodine, a standard supplement or potassium iodide at about 150 mcg/day covers requirements. Skip kelp, whose dose is unpredictable, and do not self-dose Lugol's, which delivers far more than you need and can push the thyroid either way. If you have Hashimoto's, Graves' disease or nodular goitre, talk to an endocrinologist before taking any of them.