Radioisotopes are given as a drink, in capsules that are swallowed, or by injection into a vein (as an intravenous injection). The same safety precautions are taken with this type of treatment as for other types of internal radiotherapy.

Radioactive iodine

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.

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 about four to seven days, you will be able to go home. You may need to take some special precautions after going home – you may need to avoid young children and pregnant women for a short time. The hospital staff will explain this to you.

Radioactive iodine doesn't usually cause side effects, but you may feel very tired for a few weeks after having this treatment.

Treating secondary bone cancer

Radioisotope treatment can also be given if certain types of cancer have spread to the bones (secondary cancer in the bone). A radioisotope is injected into a vein. You can be given it as an outpatient. Before you go home you will be given some simple advice to follow, as your urine and blood will be slightly radioactive for a few days. You may feel tired for a few weeks, but this type of radiotherapy treatment does not usually cause any other side effects.

You can read more about these treatments in our sections on thyroid cancer and secondary bone cancer.