Most people have heard that diabetes means having “high blood sugar.” But what does that actually mean, and why does it matter? Diabetes happens when the body has trouble controlling the amount of glucose, or sugar, in the blood.¹ Glucose is one of the body’s main sources of energy. Normally, a hormone called insulin helps move glucose out of your blood and into your cells, where it can be used for energy. In diabetes, this system does not work properly, and too much glucose stays in the blood.²
Having high blood sugar once in a while is different from having diabetes. The bigger problem with diabetes is that blood sugar can stay too high over months and years. Over time, this can quietly damage the eyes, kidneys, nerves, heart, and blood vessels, often before someone even feels it.³ So, how does this happen?
What Does Insulin Do?
After you eat carbohydrates, your body breaks them down into glucose, which enters your bloodstream. A small organ called the pancreas helps control what happens next. Inside the pancreas are cells called beta cells, which produce insulin.¹ Think of insulin as a signal telling the body, “Glucose is here! Time to use or store it.” When that signal stops working the way it should, diabetes can develop.²
Type 1 and Type 2 Diabetes Are Different
In type 1 diabetes, the immune system mistakenly attacks the beta cells in the pancreas that make insulin. As more of these cells are destroyed, the body loses its ability to produce insulin at all.¹ Without insulin, glucose builds up in the bloodstream.
Type 2 diabetes develops differently. The body becomes less responsive to insulin over time, a problem called insulin resistance. At first, the pancreas tries to make up for this by making more insulin. Over time, the body may not be able to keep up with this demand, and blood sugar begins to rise.²
This is an important distinction. Type 2 diabetes is not simply caused by eating too much sugar. It develops because the body's entire system for managing blood glucose stops working normally, which is something that can happen due to genetics, lifestyle, environment, and other factors outside a person's control.
Why is Blood Sugar Harmful?
This is where diabetes becomes more than just a number on a blood test. When blood sugar stays high for years, the extra glucose can slowly damage tissues throughout the body.³ One way this happens is through a process called glycation, when glucose attaches to proteins in the body and gradually changes how those proteins function, like rust forming on metal. Over many years, these changes can build up and affect the small blood vessels that run through organs like the eyes and kidneys.4,5
Blood vessels are especially vulnerable because they reach almost every part of the body. When those vessels are damaged, it helps explain why diabetes can affect so many organs at once.³
How Diabetes Can Affect Your Eyes
Inside the back of your eye is a thin layer of tissue called the retina, which helps your eyes detect light and see. The retina is full of tiny blood vessels that diabetes can damage over time, causing a condition called diabetic retinopathy.³
A large clinical study called the Diabetes Control and Complications Trial (DCCT) followed over 1,400 people with type 1 diabetes and compared those receiving intensive blood sugar treatment with people receiving standard care. Among people who did not yet have eye damage, intensive treatment lowered the risk of developing it by 76%. Among people who already had mild damage, it slowed progression of the damage 54%.3 This study showed that keeping blood sugar under better control can meaningfully protect the eyes over time.
How Diabetes Can Affect Your Kidneys
Your kidneys act like filters. They remove waste and extra water from your blood while keeping the things your body needs. Diabetes can slowly damage this filtering system.6
One early warning sign is a protein called albumin leaking into the urine. In a healthy kidney, albumin stays in the blood. When the kidneys are damaged, that protein can start slipping through. The same DCCT study found that people receiving intensive blood sugar treatment were significantly less likely to develop this kind of kidney damage.6
Because kidney damage often develops slowly and without obvious symptoms, it can go unnoticed for years, which is why regular checkups matter.
The Big Picture
Diabetes affects much more than blood sugar. In type 1 diabetes, the immune system destroys the cells that make insulin. In type 2 diabetes, the body becomes less responsive to insulin and eventually can’t produce enough to keep up. Both lead to glucose building up in the bloodstream.
Over many years, that extra glucose can damage blood vessels, proteins, and tissues throughout the body, affecting the eyes, kidneys, nerves, heart, and more. But these complications are not inevitable. Research has consistently shown that keeping blood sugar under better control significantly lowers the risk of long-term damage.3,6
That is why managing diabetes is about much more than getting a better blood sugar reading today. It is about protecting your whole body for the future.
What You Can Do
If you or someone in your family has diabetes or is at risk, here are some first steps you can take:
Ask your doctor for an A1C test → it shows your average blood sugar over the past three months and is one of the best tools for monitoring diabetes
If you don't have a doctor, community health centers and Federally Qualified Health Centers (FQHCs) in LA and OC offer care on a sliding scale fee
Alta Med Health Services offers free A1C testing at some local events → call (888) 499-9303 to find one of these locations
If you're uninsured or low income, Medi-Cal covers diabetes management including medications, lab tests, and nutrition counseling
Small consistent changes to diet and physical activity can make a meaningful difference → even a short walk after meals helps the body use glucose more effectively
Sources
Winer, S., Tsui, H., Lau, A., et al. (2003). Autoimmune islet destruction in spontaneous type 1 diabetes is not beta-cell exclusive. Nature Medicine, 9(2), 198–205. https://doi.org/10.1038/nm818
Weyer, C., Bogardus, C., Mott, D. M., & Pratley, R. E. (1999). The natural history of insulin secretory dysfunction and insulin resistance in the pathogenesis of type 2 diabetes mellitus. Journal of Clinical Investigation, 104(6), 787–794. https://doi.org/10.1172/JCI7231
Diabetes Control and Complications Trial Research Group. (1993). The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. New England Journal of Medicine, 329(14), 977–986. https://doi.org/10.1056/NEJM199309303291401
Monnier, V. M., Bautista, O., Kenny, D., et al. (1999). Skin collagen glycation, glycoxidation, and crosslinking are lower in subjects with long-term intensive versus conventional therapy of type 1 diabetes. Diabetes, 48(4), 870–880. https://doi.org/10.2337/diabetes.48.4.870
Genuth, S., Sun, W., Cleary, P., et al. (2015). Skin advanced glycation end products glucosepane and methylglyoxal hydroimidazolone are independently associated with long-term microvascular complication progression of type 1 diabetes. Diabetes, 64(1), 266–278. https://doi.org/10.2337/db14-0215
Diabetes Control and Complications Trial Research Group. (1995). Effect of intensive therapy on the development and progression of diabetic nephropathy in the Diabetes Control and Complications Trial. Kidney International, 47(6), 1703–1720. https://www.sciencedirect.com/science/article/pii/S008525381559008X