“When poorly controlled diabetes causes blood glucose levels that are too high or too low, you may not feel well,” explains Claudia L. Morrison, RD, outpatient diabetes program coordinator at Washington Hospital Center in Washington, D.C. “Diabetes that is poorly controlled over time can lead to complications that affect the body from head to toe.” Issues can occur with everything from one’s eyes, kidneys, and nerves to reproductive organs, blood vessels, and gums. But the most serious problems are heart disease and risk of stroke.