Downloadable forms are available online and can be accessed HERE.
For Car or Motorcycle licence: Fill in form M1 and send it to DVLA. The address is on the form.
For Bus, Coach or Lorry licence: Fill in form M1V and send it to DVLA. The address is on the form.
You can be fined up to £1,000 if you don’t tell DVLA about a medical condition that affects your driving. You may be prosecuted if you’re involved in an accident as a result.