Lugol’s Iodine Solution

• Lugol’s iodine is mainly used in the wet preparation of stool.

What are the ingredients of Lugol’s Iodine Solution?

1. Iodine powder = 5 grams.
2. Potassium iodide = 10 grams.
3. Distilled water = 100 mL.

How will you prepare Lugol’s Iodine Solution?

1. Dissolve the potassium iodide in the distilled water.
2. Add iodine crystals slowly and keep shaking the container (test tube) until these are dissolved.
3. Filter the resulting solution.
4. This is the stock solution.
5. For the working solution:
   1. Dilute the stock solution  1:5 with deionized distilled water.
6. You can use this working solution for 2 to 3 weeks and make a new working solution.

How will you make a smear of stool?

1. Make a direct wet smear.
2. A small portion of the stool is mixed with a drop of saline and Lugol iodine solution.
3. Place the cover slip on it.
4. The smears should be thin to read the newspaper under the slide.
5. Check for the amoebae and flagellates. Also, look for cysts.

Lugol’s Iodine Solution: Stool wet preparation, saline, and Lugol’s iodine

What is the storage and shelf-life of Lugol’s iodine solution?

1. Lugol’s iodine solution should be kept at room temperature and protected from light.
2. If you keep this solution under these conditions, the shelf life is roughly 26 weeks.
3. The shelf life of the working solution is approximately 3 to 4 weeks.

How will you interpret Lugol’s iodine-prepared stool slide?

1. Lugol iodine will stain the cyst of amoebae and other protozoa.
2. Iodine stain will show the details that saline preparation cannot show.
3. Trophozoites are rapidly killed by iodine and may not be identifiable.
4. Most parasites get brown coloration when stained with Lugol’s iodine solution.
5. When the stain is done correctly then, you will see the following:
   1. Cyst contains yellow-gold cytoplasm.
   2. Brown glycogen material.
   3. Paler refractile nuclei.

Important note: 

• When the iodine crystals disappear from the bottom of the bottle, the stock solution will no longer be used.
• Now, you need to replace the working solution.

Questions and answers: