The signs and symptoms of Type 1 and Type 2 diabetes can include an increase in thirst and tiredness, weight loss, frequent urination and blurred vision.
Type 1 diabetes will usually develop quickly and become obvious over a couple of weeks. Type 2 can be less easy to diagnose.
It is important to take action quickly if you do have any symptoms because prompt diagnosis and treatment reduces the chance of developing any serious health problems.
Doctors can use a range of tests to diagnose diabetes. A fasting plasma glucose (FPG) test measures blood glucose in a person who has not eaten anything for at least eight hours. An oral glucose tolerance test (OGTT) measures blood glucose after fasting for eight hours then having a glucose drink and testing two hours after. A random plasma glucose test measures blood glucose regardless of when the person last ate.
If a test indicates diabetes, it is then repeated on a different day to confirm the diagnosis.