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People in the U.S. continue to eat diets high in saturated fat and get little exercise. And more and more of them are being diagnosed with type 2 diabetes. While many people with diabetes make lifelong lifestyle changes to control their blood sugar, others may not understand that eating too much sugar when they have diabetes can lead to further complications years down the road—especially for the eyes, kidneys and nerves in the arms, legs, hands and feet.

In type 2 diabetes, the cells in the body stop responding to a hormone called insulin. Normally, insulin tells cells to take in, or transport, blood sugar (glucose) into each cell. But in people with diabetes, the body stops listening to the insulin message over time and becomes insulin resistant. Insulin resistance leads to a buildup of glucose in the blood (high blood sugar, also called hyperglycemia). People who have trouble keeping their blood sugar in healthy ranges develop organ damage over time—but not all organs are affected equally. Some organ systems take more of a hit than others when it comes to diabetes complications.

In a healthy body, the eyes need a constant supply of high levels of glucose to function. There is normally a large amount of glucose being transported into cells in the part of the eye that relays light signals to the brain (retina). However, in someone with consistently high blood sugar, the retina can’t stop more glucose from entering the cells. Too much sugar in the retinal cells damages the blood vessels and can lead to a complication known as diabetic retinopathy. People with this condition may have blurred vision, see dark spots in their field of vision (floaters) or have permanent loss of vision.

Cells in the kidney (mesangial cells) and nerve cells in the arms and legs (peripheral nerves) also require high amounts of energy from glucose to function in a normal body. When there is too much sugar in the blood, damage can occur. Diabetic nephropathy is a type of kidney disease related to diabetes. Diabetes-related neuropathy—numbness, pain or tingling in the hands or feet—affects the nerves.

Diabetes-related complications can be an unwelcome burden to people with diabetes. However, keeping blood glucose levels under control through diet and exercise—and medications, if your doctor prescribes them—can help delay or even prevent the onset of these complications.

Sadie Dierschke is a PhD candidate in the biomedical sciences program at Penn State College of Medicine. Her studies in the lab of Michael Dennis, PhD, include understanding how translational control of retinal gene expression contributes to the development of diabetic retinopathy. ​