Lugol’s Iodine 2% vs 5% vs 15% | Which Strength To Choose?

The 5% solution is the only strength with a documented US drug label: 5% iodine and 10% potassium iodide, sold as a topical antiseptic.

A 15% bottle next to a 5% bottle looks like three times the punch and may contain less elemental iodine. The percentages aren’t a strength scale—they don’t all measure the same thing, only one has a US drug label, and “maximum strength” is marketing, not a regulatory status.

What Does The 5% Label Actually Mean?

The 5% strength is the only one with a documented US formulation: 5% elemental iodine plus 10% potassium iodide, weight/volume—0.05 g iodine and 0.100 g potassium iodide per milliliter. An NIH-indexed medication-safety report lists it as 50 mg/mL iodine and 100 mg/mL potassium iodide.

DailyMed, the National Library of Medicine’s drug label database, carries it as LUGOLS STRONG IODINE, an aqueous iodine and potassium iodide solution labeled a topical antiseptic, described as a germicide and fungicide. The listing notes it is preservative-free and that iodide preparations are contraindicated in people with known sensitivity. The DailyMed label for strong iodine solution also carries the FDA disclaimer: the drug has not been found by FDA to be safe and effective, and its labeling has not been approved by FDA.

That disclaimer is the sentence sellers leave out. The 5% product is a recognized over-the-counter skin antiseptic, not a vetted oral supplement, and swallowing it steps outside the labeled use.

Lugol’s Iodine Strengths: What The Labels Do And Don’t Say

A 2% or 15% bottle has no authoritative US drug label pinning down its formulation, intended use, drop size, or FDA status, so the front percentage can’t be compared to 5% without the full ingredient panel.

One product sold as 15% reports iodine under 5% and potassium iodide under 10%, suggesting the 15% may be a combined-ingredient figure or the seller’s definition rather than 15% elemental iodine. At least one 15% listing states it cannot ship to the United States, so availability shifts by seller and country. Treat 2% products the same way: separate commercial formulations until the maker publishes verified elemental-iodine and potassium-iodide numbers.

Read the table as questions, not a ranking. Elemental iodine percentage, total iodine content, and drop volume are three different numbers; mixing them up is the most common buying error.

Who Should Avoid Concentrated Iodine Drops?

Get a clinician’s answer before opening the bottle if you have thyroid disease, are pregnant or breastfeeding, have kidney disease, react badly to iodine, or take medicines that affect thyroid function or potassium balance. Product safety notices advise the same.

Excess iodine and iodide can disrupt thyroid function. Reported effects of iodide preparations include stomach and gut symptoms, rash, metallic taste, neck or throat swelling, irregular heartbeat, and neurologic symptoms.

A drop is not a standardized dose, so concentration, drop size, and total daily amount must come off that specific label. Never take a topical antiseptic by mouth unless a clinician prescribes it. Don’t swap it for an FDA-regulated iodine supplement, and don’t use it for thyroid disease, infection, radiation exposure, or iodine deficiency without a clinician’s protocol. Keep bottles out of children’s reach, away from eyes, tightly closed in a cool, dark spot; iodine stains fabric and counters.

Anyone comparing bottles can use our tested Lugol’s iodine product roundup to line current labels up against this list.

What the bottle is for decides the pick.

• Skin antiseptic duty, clinician-directed: the 5% iodine and 10% potassium iodide product with external use on its label.
• Dietary iodine: an FDA-regulated supplement or a preparation a clinician names, never a dropper of antiseptic.
• A 2% or 15% bottle: only after the maker states elemental iodine and potassium iodide per milliliter, and only with clinician sign-off.