Symptoms usually come on suddenly and strongly. Typically the most prominent symptoms are excessive urination and extreme thirst. This is because the increased glucose in the blood causes the kidneys to create more urine than usual. Losing more fluid in the urine makes a person dehydrated. And dehydration leads to great thirst. Children may start to wet the bed again.
Weight loss, with no loss of appetite, also is common. The weight loss is due in part to dehydration. Water has weight. Imagine holding a gallon jug of water: it weighs about eight pounds. People with new, uncontrolled type 1 diabetes can lose a gallon of water from dehydration.
Other common symptoms are weakness, fatigue, confusion, nausea and vomiting. Dehydration can cause weakness, fatigue and confusion. Another cause of these symptoms, along with nausea and vomiting, is a condition called ketoacidosis.
Ketoacidosis occurs because cells can't the glucose they need for energy. So the cells have to use something else. As an alternative fuel, the liver produces substances called ketones. Ketones are a kind of acid. When they build up in the blood, it's called ketoacidosis. Ketoacidosis can cause heart problems and affect the nervous system. Within hours, it may put a person at risk of coma or death.
Even after it is diagnosed and treatment is begun, type 1 diabetes can affect all body systems. It is less likely to damage the body, and cause symptoms, if the blood sugar levels are well controlled by treatment.
The serious and potentially life-threatening complications that can occur with type 1 diabetes include:
Eye damage (retinopathy) — Tiny blood vessels at the back of the eye are damaged by high blood sugar. Caught early, retinopathy can be stopped by tightly controlling blood sugar and laser therapy. If blood sugar remains high, retinopathy eventually causes blindness.
Nerve damage (neuropathy) — High blood sugar can damage nerves, leading to pain or numbness of the affected body part. Damage to nerves in the feet, legs and hands (peripheral neuropathy) is most common. Nerves that control body functions, such as digestion and urination, also can be damaged.
Foot problems — Sores and blisters commonly occur on the feet of people with diabetes. If peripheral neuropathy causes numbness, a sore may not be noticed. It can become infected. Blood circulation can be poor, leading to slow healing. Left untreated, a simple sore can lead to gangrene. Amputation may be necessary.
Kidney disease (nephropathy) — High blood sugar can damage the kidneys. If blood sugar remains high, it can lead to kidney failure.
Heart and artery disease — People with type 1 diabetes are more likely to have heart disease, strokes and problems related to poor circulation.
Diabetic ketoacidosis — This occurs when ketones are made by the body as a substitute for glucose. Symptoms include:
Nausea and vomiting
Coma and death (if ketoacidosis is left untreated)
Hypoglycemia — Low blood sugar (hypoglycemia) can result from insulin treatment (see Treatment section, below). Hypoglycemia may occur if too much insulin is taken or meals are skipped. Symptoms include:
Blurry or double vision
Hypoglycemia can lead to coma if it is not corrected by eating or drinking carbohydrates. Glucagon is a substance that makes the liver release glucose into the bloodstream. An injection of glucagon can also correct hypoglycemia.