Untreated or poorly controlled diabetes can lead to a number of serious health problems, including heart and blood vessel disease. Even if you have your diabetes under control, you're at greater risk for heart attack and stroke than someone who does not have diabetes. This is because diabetes damages blood vessels and increases triglyceride levels. It also decreases HDL - the good cholesterol. Many people with diabetes also have high blood pressure and are overweight. These are two more risk factors for heart disease.