What is the first indicator of Type I diabetes?

The first indicator of Type I diabetes is often increased thirst, also known as polydipsia, which arises as a result of elevated blood glucose levels leading to dehydration. In Type I diabetes, the body's immune system attacks insulin-producing cells in the pancreas, causing a lack of insulin. As glucose builds up in the bloodstream and cannot be adequately used for energy, the kidneys excrete the excess glucose into the urine. This process draws water out of the body and results in increased thirst.

Ketoacidosis, while a serious and acute complication that can occur in individuals with Type I diabetes, usually manifests later in the disease process when the lack of insulin becomes critical. It is characterized by high levels of ketones, which can lead to altered blood pH and requires immediate medical attention. Weight gain is generally not associated with Type I diabetes, as individuals often experience weight loss due to energy depletion. Blurred vision can occur as a symptom of hyperglycemia and may also appear later, but it is not the primary indicator of the onset of the condition. Therefore, increased thirst is the correct first indicator of Type I diabetes.