糖尿病（Diabetes mellitus或diabetes）是指會影響身體使用血糖 （blood glucose，一般稱為blood sugar）的一類疾病。葡萄糖對於健康至關重要，因為它對於組成肌肉和組織的細胞而言是重要的能量來源。它也是腦部的主要能量來源。
Chronic diabetes conditions include type 1 diabetes and type 2 diabetes. Prediabetes is a condition in which your blood sugar levels are higher than normal, but not high enough to be classified as diabetes and may be reversible. Gestational diabetes occurs during pregnancy but may resolve after the baby is delivered.
If you have diabetes, no matter what type, it means you have too much glucose in your blood. Too much glucose can lead to serious health problems.