More than half a million people with diabetes in the UK are estimated to be undiagnosed. A further 11 million people are believed to be at risk of developing the disease.
There are two types of diabetes: type 1 where the body suddenly stops producing insulin, a hormone which regulates blood sugar levels and type 2 where the body doesn't produce enough insulin or the body becomes resistant to it.
Although the symptoms of type 1 diabetes are usually obvious because they start suddenly and result in rapid weight loss and extreme thirst and tiredness, the symptoms of type 2 diabetes are slower and more insidious, and therefore harder to spot.
'Unfortunately a lot of the symptoms of type 2 diabetes such as tiredness and fatigue and frequent urination can be confused with other medical conditions,' says Libby Dowling, clinical adviser to the charity Diabetes UK.
'Equally the symptoms of type 2 diabetes can develop so slowly over time that you might not notice them - you may just put tiredness for instance down to getting older or having kids and a busy job.'