MODEL RELEASED. Diabetic patient being shown a home blood glucose tester by her doctor. The device (centre left) measures the levels of glucose in the patient's blood. Diabetes mellitus is a condition in which the pancreas does not produce enough of the hormone insulin, which regulates blood sugar levels. Diabetic patients need to regulate their diet and check their blood sugar levels to ensure that they don't fall outside healthy parameters. Both low blood sugar (hypoglycaemia) and high blood sugar (hyperglycaemia) are dangerous, causing coma and even death.