Lugol's Solution

We evaluated 154 human studies on Lugol's solution, including 11 randomised controlled trials and 2 meta-analyses or systematic reviews; the controlled studies include 6,593 participants in total. As of 3 October 2026.

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1. What Is Lugol's Solution? Occurrence, Origin and Forms

Lugol's solution is an aqueous solution of elemental iodine and potassium iodide, classically with 5% iodine and 10% potassium iodide; weaker dilutions are also in use. Closely related is the saturated solution of potassium iodide (SSKI). Both supply iodine in amounts far above the daily requirement from food.

The solution itself does not occur in nature. Its component iodine comes from seawater, seaweed, iodine-rich brines and the mother liquor of Chilean saltpetre production.

It is made by dissolving iodine in a potassium iodide solution. The potassium iodide makes the otherwise barely water-soluble iodine soluble.

Forms and Preparations Studied

• Lugol's solution at classic strength and in dilutions
• Saturated solution of potassium iodide (SSKI) and high-dose potassium iodide
• Potassium iodide tablets to protect the thyroid from radiation
• Molecular iodine (I2) and iodine in the milligram range, for example for breast complaints

Not covered on this page:

• Iodised salt and iodine supplements in the microgram range, for example in pregnancy or iodine deficiency → Iodine
• Povidone-iodine and other iodine disinfectants
• Lugol's solution as a stain in endoscopy, colposcopy or dentistry
• Radioiodine therapy (iodine-131) as a treatment in its own right, and iodinated contrast media
• Potassium iodide as an enhancer of photodynamic therapy

2. What Does Lugol's Solution Do? Results by Area

How to read the table: counted are human studies whose results concern the area. “High” means at least one meta-analysis and two controlled studies showing improvement, or at least three controlled studies of which three quarters show improvement, with at least 300 participants in total. “Moderate” means at least two controlled studies showing improvement, as a majority, or one meta-analysis alongside controlled studies. “Low” means one controlled study showing improvement. Where an area has no controlled study, the strength of evidence is at most “low” (result “reviews only” or “observational data only”). Everything else is “unclear”. A study counts as showing improvement when at least half of its outcomes in this area improved. Reviews of combination products do not count as meta-analyses; results that only describe side effects or shares of users do not count as an effect. The same study is counted only once.

3. What the Studies Show in Detail

Lugol's Solution, Hyperthyroidism and Graves' Disease: Human Studies

In Graves' disease before thyroid surgery, preoperative administration of Lugol's solution lowered thyroid hormones in a randomized study 9; a controlled study found the same for potassium iodide 25. A randomized and a controlled study also found lower thyroid blood flow 1123. In a randomized study, thyroid hormones before surgery were too low in just over a third of those treated with Lugol's solution 13. A controlled study with saturated potassium iodide solution (SSKI) found no difference in thyroid status and in the frequency of hyper- and hypofunction six weeks after radioiodine 15. The strength of evidence is moderate: nine controlled studies, predominantly with small participant numbers and without information on manufacturer funding, in which Lugol's solution was mostly investigated preoperatively and partly in combination with antithyroid drugs. It remains open whether preoperative administration actually improves the surgical course or the longer-term disease course.

Further studies in this area: 25 27 30 33 36 39 40 41 43 44 45 48 49 51 53 55 56 57 58 59 61 64 65 66 67 71 72 73 75 76 78 79 80 81 82 83 84 87 93 94 95 98 100 101 106 107 111 113 114 116 118 122 123 129 130 136 137 138 140 143

Lugol's Solution and Preparation for Thyroid Surgery: Human Studies

In thyroid surgery, preoperative administration of Lugol's solution showed lower intraoperative blood loss in two randomized studies 711. Three randomized studies found no difference in blood loss compared with preparation without Lugol's solution 6913. The strength of evidence is moderate: the seven controlled studies with a total of 121 participants are opposed by 34 further works, which are predominantly designed as case series or observational studies. Mostly the classical Lugol's solution was investigated; for saturated potassium iodide solution (SSKI) only one observational study is available 35. It remains open which patient groups and which dosage regimen actually benefit, since the comparison groups and concomitant medications vary greatly between the studies.

Further studies in this area: 29 30 31 32 34 35 38 42 43 49 58 62 68 69 70 83 86 89 90 99 102 103 106 109 113 114 115 123 124 125 134 142 150

Lugol's Solution, Breast Tissue and Breast Pain: Human Studies

In breast pain and fibrocystic changes, a randomized controlled trial with molecular iodine showed improvement in pain, tenderness and nodularity compared with placebo 3. The strength of evidence is moderate; molecular iodine (I2) was investigated, not Lugol's solution or potassium iodide. The exact dose, the duration and the transferability to other iodine preparations remain open.

Lugol's Solution and Thyroid Protection from Radiation: Human Studies

A systematic review of potassium iodide tablets after nuclear accidents found evidence of a reduced risk of thyroid cancer in children, with low quality of evidence 1. A controlled study (not randomized) in healthy volunteers found a reduction in thyroid dose for high-dose potassium iodide 17. In the efficacy comparison, high-dose potassium iodide did not perform better than sodium perchlorate 17. Potassium iodide tablets and high-dose potassium iodide were studied; efficacy and risk in children, in iodine deficiency and with longer administration remain open.

Further studies in this area: 149

Lugol's Solution and Infections: Human Studies

For infections, a comparison with placebo or other agents is lacking: A randomized study in patients with cutaneous sporotrichosis compared only one and three daily doses of saturated potassium iodide solution (SSKI) and found no difference in healing and relapse 12. A systematic review of oral high-dose potassium iodide in cutaneous sporotrichosis comes to no clear efficacy result 2. The strength of evidence is therefore unclear; both works studied saturated potassium iodide solution as an oral preparation. It remains open whether and at what dosage potassium iodide works at all in these infections.

Further studies in this area: 88 91 96 97 104 105 108 110 112 117 120 121 126 127 128 147 148

Lugol's Solution: Further Outcomes in Studies

In this area, the studies show a mixed picture with low strength of evidence. A randomized study with preoperative Lugol's solution in Graves' disease found no difference in sonographically measured blood flow and vessel density in the tissue 9. In cutaneous sporotrichosis, the side effects did not differ between once and three times daily administration of saturated potassium iodide solution 12. A controlled study with saturated potassium iodide solution in people with previous iodine-induced hyperthyroidism found no difference in T4 and T3, but in some the TSH rose significantly 20. A controlled study found that iodine from potassium iodide was better absorbed and excreted than from a kombu preparation 19. In nodular goiter, a controlled study under Lugol's solution found no change in thyroid blood flow 23. Lugol's solution, saturated potassium iodide solution and high-dose potassium iodide were studied; statements on duration, comparison groups and transferability remain open, since the strength of evidence is low and several studies were not randomized.

Further studies in this area: 22 23 30 44 45 46 47 49 50 51 63 64 67 68 73 76 80 82 84 86 89 92 97 98 101 106 108 111 119 122 129 133 135 141 145

4. How Is Lugol's Solution Dosed? Preparation, Dose and Duration in Studies

The classical Lugol's solution, saturated potassium iodide solution (SSKI), high-dose potassium iodide and molecular iodine (I2) were investigated. Lugol's solution was mainly tested preoperatively in Graves' disease and thyroid surgery, sometimes in addition to radioiodine therapy. SSKI and high-dose potassium iodide were used in thyroid hyperfunction, after radioiodine, in radiation exposure, in cutaneous sporotrichosis and in studies on iodine excretion; the doses are shown in the table.

5. Is Lugol's Solution Safe? Side Effects in Studies

The studies predominantly report good tolerability of the iodine doses, with frequently mild and transient adverse events 3512. With saturated potassium iodide solution, adverse effects occurred frequently but mildly in a controlled study, with no difference between once and three times daily administration 12. In several controlled studies, hypothyroidism or excessively low thyroid hormones occurred under high-dose iodine, sometimes detectable only by an elevated TSH value 131620. After thyroid surgery, patients with Lugol's solution needed short-term calcium more frequently in a large cohort study 29. In a further cohort study, vocal cord nerve paralysis and parathyroid hypofunction occurred more frequently, while neck bruising occurred less frequently 31. Details are shown in the table.

6. What Remains Open: Limits of the Evidence

• The controlled studies on thyroid hyperfunction and thyroid surgery mostly have small participant numbers and no information on manufacturer funding.
• The comparison groups and concomitant medications differ greatly between the studies, so it remains unclear which patient groups and dosage regimens benefit.
• For saturated potassium iodide solution (SSKI) in thyroid surgery, only one observational study is available.
• For breast tissue and breast pain, molecular iodine (I2) was investigated, not Lugol's solution or potassium iodide; dose and duration remain open.
• For thyroid protection after radiation exposure and in infections, the strength of evidence is unclear, and data on children, iodine deficiency and longer-term administration are lacking.

7. Bottom Line: What Is Established About Lugol's Solution

Lugol's solution and related high-dose iodine preparations are best studied for preoperative preparation in Graves' disease and thyroid surgery. There, in several controlled studies, they lowered thyroid hormones and thyroid blood flow and sometimes reduced blood loss, while other controlled studies found no difference in blood loss and operating time. The strength of evidence is moderate, the studies are predominantly small and without information on manufacturer funding.

For breast pain and fibrocystic changes, a randomized controlled trial with molecular iodine showed improvement compared with placebo, although Lugol's solution was not investigated. For thyroid protection after radiation exposure and in infections such as cutaneous sporotrichosis, the strength of evidence is unclear because comparisons with placebo are lacking or the evidence is weak. Overall, effect and risk depend strongly on dose, preparation and concomitant treatment.