Radioisotopes are given as liquids, in capsules that are swallowed, or as a drink; or by injection into a vein (as an intravenous injection). The most common type of radioisotope treatment is radioactive iodine. It is used to treat tumours of the thyroid gland, and is given as capsules. The same safety precautions are taken with this type of treatment as for other types of internal radiation treatment.

Any radioactive iodine that is not absorbed by the thyroid will be passed from the body in sweat and urine. You need to drink plenty of fluids during your treatment as this helps to flush the iodine out of the body. The amount of radiation in your body will be checked regularly and as soon as it falls to a safe level, after a few days, you will be able to go home. You might need to take some special precautions for a short time after going home – and might need to avoid young children and pregnant women for a short time. The hospital staff will explain this to you.

Radioactive iodine does not usually cause side effects, but you might feel very tired for a few weeks after having this treatment.