Lugols solution is commonly available in different potencies of (nominal) 1%, 2%, 5% or 10%. Iodine concentrations greater than 2.2% are subject to US regulations. If the US regulations are taken literally, their 2.2% maximum iodine concentration limits a Lugols solution to maximum (nominal) 0.87%.
The most commonly used (nominal) 5% solution consists of 5% (wt/v) iodine () and 10% (wt/v) potassium iodide (KI) mixed in distilled water and has a total iodine content of 126.4 mg/mL. The (nominal) 5% solution thus has a total iodine content of 6.32 mg per drop of 0.05 mL; the (nominal) 2% solution has 2.53 mg total iodine content per drop.
Potassium iodide renders the elementary iodine soluble in water through the formation of the triiodide () ion. It is not to be confused with tincture of iodine solutions, which consist of elemental iodine, and iodide salts dissolved in water and alcohol. Lugol's solution contains no alcohol.
Other names for Lugol's solution are  (iodine-potassium iodide); Markodine, Strong solution (Systemic); and Aqueous Iodine Solution BP.