According to Blood Pressure UK, there are a number of treatments available, including:
Diuretic medicines – these increase the amount of fluid removed by your kidneys and this can help to get rid of any excess fluid from the body.
This removes the build-up of fluid from the tissues in your ankles.
If the ankle swelling is due to taking calcium channel blockers, reducing the dose of your medicine will usually help. Or, if your blood pressure is not fully controlled, your doctor may prescribe you a diuretic to help lower your blood pressure further and remove the excess fluid.
Sitting with your legs lifted up. This lets your blood flow more freely and should help reduce the swelling.
Reducing salt intake should also help to reduce the swelling.
However, if the swelling is a sign of an underlying disease, the disease itself requires separate treatment.