Cause

Complications from type 2 diabetes may be caused by one or all of the following:

• Damage to the lining of the blood vessels throughout your body, contributing to development of plaque
• Damage to the nerves that reduces or blocks their ability to send messages to your organs, legs and arms, and other parts of your body. Nerve damage can also affect information getting back to the brain.
• Changes to your immune system that decrease your body's ability to fight infection
• Damage to the filtering cells in the kidneys, causing a buildup of toxins

The damage results from hormonal and cellular changes caused by excess sugar (glucose) in your body.

Symptoms

Your symptoms depend on which complication of type 2 diabetes you have.

Eye disease

Diabetic retinopathy in its early stages does not noticeably affect your vision. But if it's not treated early, diabetic retinopathy can cause symptoms such as:

• Blurred or distorted vision or difficulty reading. This may be caused by macular edema or other changes in the retina. High blood sugar levels may cause temporary blurred vision, which will clear up after the level returns to your target range. It may take several hours after blood sugar has been corrected for your vision to return to normal. Contact your doctor if vision changes last 12 to 24 hours.
• Floaters or flashes of light in your field of vision. These symptoms are caused by retinal detachment or bleeding into the vitreous gel.
• Partial or total loss of vision, or a shadow or veil across your field of vision. These symptoms also are caused by retinal detachment or bleeding in the vitreous gel.
• Pain in your eye, which can be caused by neovascular glaucoma.

For more information, see the topic Diabetic Retinopathy.

Heart and large blood vessel disease

You may develop macrovascular disease because of diabetes, but you may not have any symptoms until you have a heart attack or stroke or develop peripheral arterial disease.

Symptoms of coronary artery disease include:

• Chest pain.
• Shortness of breath with exertion.
• Nausea, and discomfort that feels like heartburn.
• Fatigue.

Symptoms of transient ischemic attack (TIA)—a temporary interruption of blood flow to part of the brain and a warning sign of an impending stroke—include:

• Weakness on one side of the body, or inability to move a part or all of one side of the body, such as the face, arm, and leg.
• Numbness, tingling, or a feeling of heaviness.
• Difficulty speaking or understanding words.
• Loss of vision or changes such as blurring or double vision.

Symptoms of peripheral arterial disease include:

• Intermittent claudication, a tightness or squeezing pain in the calf, thigh, or buttock during exertion, such as walking.
• Decreased leg strength and poor balance when standing.
• Cold and numb feet or toes.
• Loss of hair on the feet or legs.

Erection problems (erectile dysfunction) can be an early warning sign of blood vessel disease and may indicate a higher risk of heart disease.

For more information, see the topics Coronary Artery Disease, Heart Attack and Unstable Angina, Peripheral Arterial Disease of the Legs, Stroke, and Transient Ischemic Attack (TIA).

Nerve damage

Symptoms of peripheral neuropathy (affecting the nerves that control sensation, touch, and movement) include:

• Tingling, numbness, tightness, burning, or shooting or stabbing pain that starts in the feet and may spread to the legs, hands, and arms. Usually, symptoms occur in the toes first and are worse in the evening. Ulcers and infection may develop in the feet. Bone and joint deformities also can develop, especially in the feet (Charcot foot).
• Greatly reduced or greatly increased sensitivity to temperature changes and a sense of pain with light touch.
• Weakness and loss of balance and coordination.

Symptoms of autonomic neuropathy (affecting the nerves that control internal functions) include:

• Digestive problems, such as frequent bloating, belching, constipation, nausea and vomiting, diarrhea, and abdominal pain. These symptoms may mean that you have gastroparesis.
• Temperature regulation problems, including profuse sweating on your chest, face, or neck at night or while eating certain foods, such as spicy foods and cheese. Or you may have reduced sweating, especially in your feet and legs.
• Difficulty sensing when your bladder is full or difficulty emptying your bladder completely.
• Sexual problems, such as erection problems in men and vaginal dryness in women.
• Dizziness, weakness, or fainting when you stand or sit up from a reclining position (orthostatic hypotension). If you have coronary artery disease, you may not experience chest pain with a heart attack.
• Difficulty knowing when your blood sugar is low (hypoglycemia unawareness).

Symptoms of focal neuropathy (affecting a single nerve) usually start suddenly and may include:

• Pain, weakness, and movement difficulty in a single area of your body, such as your face.
• Pain in and around one of your eyes (if neuropathy affects the nerves that control eye muscles), difficulty moving your eyes, and double vision.

For more information, see the topic Diabetic Neuropathy.

Kidney disease

The only sign of diabetic nephropathy in its early stage is very small amounts of protein leaking into the urine (microalbuminuria). This can be detected only by a urine test for microalbumin. Treatment at this stage can delay progression and prevent symptoms from developing. But if your kidney disease progresses, you may have:

• Increasing tiredness or fatigue.
• Swelling (edema) in your feet and legs and later throughout your body.
• Increasing blood pressure.
• Large amounts of protein leaking into your urine (macroalbuminuria). Frothy or foamy urine can be a sign of excess protein in your urine.
• High levels of cholesterol and triglycerides in your blood.

Kidney disease increases your risk of forming blood clots. As nephropathy gets worse, kidney failure develops. Your kidneys become severely damaged. And they may not eliminate insulin from your body as quickly. Insulin can then build up in your blood and cause low blood sugar. Your insulin dose will have to be adjusted. You also may need to lower the dose of, or stop taking, other medicines. For instance, the oral diabetes medicine metformin can be deadly in people who have kidney failure.

For more information, see the topic Diabetic Nephropathy.