The Vocabulary of Iodine Supplements: A Glossary

Molecular iodine, iodide, nascent, tincture, Lugol's — the terminology around iodine products can be confusing. This glossary post defines the terms you'll encounter while shopping for a liquid iodine supplement.

Iodine Forms

• Iodine (I₂): the elemental form, also called molecular iodine. Dark crystals that give solutions an amber-brown color.
• Iodide (I⁻): the negatively charged ion of iodine, found in salts such as potassium iodide. The form the body absorbs.
• Iodate (IO₃⁻): an oxygen-containing form of iodine. Potassium iodate is used to iodize salt in many countries.
• Triiodide (I₃⁻): forms when iodine and iodide meet in water. It's what keeps iodine dissolved in Lugol's iodine.
• Potassium iodide (KI): a white salt that dissolves easily in water. See Molecular Iodine vs. Iodide.

Product Types

• Lugol's iodine / Lugol's Solution: a water-based solution of iodine and potassium iodide, first described in 1829. See Lugol's Solution.
• Liquid iodine: a broad term for any iodine supplement in liquid form.
• Nascent iodine: a marketing term, usually for glycerin-based iodine drops. See Nascent Iodine 101.
• Tincture of iodine: iodine dissolved in alcohol, traditionally used on the skin, not taken by mouth. See Iodine Tincture vs. Iodine Solution.
• Povidone-iodine: iodine bound to a polymer, used as a topical antiseptic.
• Kelp supplements: dried seaweed in tablet or powder form, with naturally occurring iodine that varies from batch to batch.

Strength and Measurement

• Percentage (%): the concentration of a solution. Higher percentage, more iodine per drop. See Reading Your Bottle's Percentage Label.
• mcg (microgram): one-millionth of a gram. Dietary iodine recommendations are given in micrograms.
• mg (milligram): one-thousandth of a gram, or 1,000 mcg.
• Drop: the unit used for liquid servings; size depends on the dropper. See Drop Size Variation.

Intake Terms

• RDA (Recommended Dietary Allowance): the daily intake that meets the needs of nearly all healthy people. For adults, 150 mcg of iodine.
• UL (Tolerable Upper Intake Level): the highest daily intake unlikely to cause harm for most people. For adults, 1,100 mcg of iodine.
• Daily Value (%DV): the reference amount used on Supplement Facts labels.

Quality Terms

• USP grade: meets United States Pharmacopeia standards. See What Does USP Grade Mean?
• COA (Certificate of Analysis): a document showing test results for a batch. See How to Read a COA.
• Assay: a test that measures how much of a substance is present.
• Titration: the classic lab method for measuring iodine. See The Basics of Titration.
• Amber glass: brown-tinted glass that blocks most UV light. See Why Amber Glass Matters.

Body Terms

• Thyroid: the gland in the neck that uses iodine to make hormones.
• T4 (thyroxine) and T3 (triiodothyronine): the two main thyroid hormones, carrying four and three iodine atoms.
• TSH: thyroid-stimulating hormone, released by the pituitary gland to regulate the thyroid.

Frequently Asked Questions

Should I talk to a doctor before starting?
Yes. Anyone considering a new supplement — especially one involving iodine — should check in with a healthcare provider first, particularly if pregnant, nursing, or managing a thyroid condition or thyroid medication.

Where can I read the full picture on usage once I know the terms?
See our complete guide to Lugol's Solution usage and protocols.

Shop Lugol's Solution — the traditional, trusted way people have supported their iodine intake for over 200 years.

Jessica Bennett writes about clean, ingredient-conscious living for the Iodine Journal.

This article is for general educational purposes only and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease, and is not a substitute for advice from a qualified healthcare provider — especially if you are pregnant, nursing, taking thyroid medication, or managing a thyroid condition.