The classic symptoms of type 1 diabetes are sudden in onset and include:
- Polyuria (excessive urination) as the kidneys attempt to rid the body of excess glucose
- Polydypsia (excessive thirst) due to the dehydration associated with polyuria
- Polyphagia (excessive hunger) due to starvation of the body's cells as substrates do not enter without insulin action
- Weight loss due to the catabolic effect of lack of insulin
- Other symptoms include weakness, dehydration, electrolyte imbalance and ketoacidosis

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