- Years of high blood sugar can damage small blood vessels and nerves in the eyes, kidneys and feet, and large arteries to the heart and brain.
- These complications develop slowly and can be prevented, delayed, or treated early when found by routine checks.
- In the UKPDS, each 1% lower A1C was linked with a 37% lower risk of small-vessel complications.
The word “complications” can sound frightening. The reassuring truth is that most of them take many years to develop, most give early warning signs on simple tests, and most can be slowed or stopped. People with type 2 diabetes today have far lower rates of complications than a generation ago, thanks to better treatments and regular screening.
Where diabetes can cause damage
Organs to protect
Eyes (retinopathy)
High glucose weakens the tiny blood vessels at the back of the eye. Early changes cause no symptoms, but can be seen on a retinal exam and treated before vision is affected. Diabetes also raises the risk of cataracts and glaucoma.
Kidneys (diabetic kidney disease)
The kidneys’ filters are made of fine blood vessels. Damage first shows as small amounts of protein (albumin) leaking into the urine, long before you feel anything. Blood pressure control and kidney-protective medicines, such as SGLT2 inhibitors, ACE inhibitors or ARBs, and in some cases finerenone or a GLP-1 medicine, can slow it considerably.
Nerves (neuropathy)
Nerve damage most often starts in the feet with tingling, burning, pain or numbness. Numb feet are dangerous because injuries go unnoticed. Nerves to the stomach, bladder, heart and sexual organs can also be affected.
Feet
Numbness plus poor circulation means a small blister can become an ulcer or infection. Daily foot checks and good footwear prevent most serious problems.
Heart and blood vessels
This is the most important complication of all. We cover it in Diabetes and Your Heart.
Gums
Gum disease is more common and more severe with diabetes, and it can make blood sugar harder to control. Regular dental visits help both.
Why control makes such a difference
The UK Prospective Diabetes Study followed thousands of people with newly diagnosed type 2 diabetes for years. It found a steady relationship: the lower the average A1C, the lower the risk.
UKPDS 35, BMJ 2000. Observational associations across the study population.
Blood pressure control mattered just as much. And the benefits of good early control lasted for years afterward, a “legacy effect”, which is a strong reason to act early.
Your yearly check-up list
| Check | How often | What it finds |
|---|---|---|
| A1C | 2–4 times a year | Average blood sugar |
| Blood pressure | Every visit | Heart, kidney and eye risk |
| Cholesterol (lipid panel) | At least yearly (or as advised) | Heart and stroke risk |
| Kidney tests: urine albumin-to-creatinine ratio and eGFR blood test | At least yearly | Early kidney damage |
| Dilated eye exam or retinal photo | Every 1–2 years | Retinopathy before vision changes |
| Comprehensive foot exam | At least yearly; feet checked at every visit if at risk | Loss of sensation, poor circulation |
| Dental exam | Every 6–12 months | Gum disease |
What you can do every day
- Keep blood sugar, blood pressure and cholesterol near the goals you agreed with your care team.
- Check your feet daily for cuts, blisters, redness or swelling. Use a mirror or ask someone to help.
- Wear well-fitting shoes and never walk barefoot if your feet are numb.
- Take medicines as prescribed, including blood pressure and cholesterol tablets. See Taking Your Medicines Consistently.
- Do not smoke, stay active, and brush and floss daily.
- Report changes early: vision changes, foot wounds that do not heal, swelling, or new numbness.
Common questions
Can diabetic eye disease be treated?
Yes, especially when found early. Treatments include laser therapy, injections into the eye and, when needed, surgery. Early retinopathy often causes no symptoms, so regular screening is essential. Good control of blood sugar and blood pressure slows it down.
Is kidney damage from diabetes reversible?
Early kidney changes can sometimes improve, and progression can be slowed considerably with blood pressure control, ACE inhibitors or ARBs, SGLT2 inhibitors and, in some cases, finerenone or a GLP-1 medicine. The key is annual urine albumin and eGFR testing so treatment can start early.
What should I do if I find a sore on my foot?
Do not wait. Keep it clean and covered, stay off it as much as possible, and contact your doctor, nurse or podiatrist the same day, especially if there is redness, swelling, warmth, discharge or a bad smell. Never try to cut corns or calluses yourself.
- Complications develop slowly and are largely preventable.
- Yearly kidney, eye and foot checks catch problems early.
- Every improvement in A1C and blood pressure lowers risk.
- Next: Type 2 diabetes medicines explained.
Type 2 Diabetes Basics: all 18 articles
- What Is Type 2 Diabetes?
- Type 2 Diabetes Risk Factors
- Early Signs and Symptoms
- How Type 2 Diabetes Is Diagnosed
- A1C vs Blood Glucose
- Diabetes and Your Heart
- Preventing Long-Term Complications
- Type 2 Diabetes Medicines Explained
- GLP-1 Medicines: What to Expect
- Taking Your Medicines Consistently
- When Your Diabetes Changes
- Digital Tools: Meters, CGMs and Apps
- How to Read a Nutrition Label
- Carb Counting Made Simple
- Small Food Swaps for Lower Blood Sugar
- Travelling With Diabetes
- Diabetes Distress and Depression
- Caring for Someone With Type 2 Diabetes
Sources
- UK Prospective Diabetes Study Group; Stratton IM, et al. Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35). BMJ. 2000;321:405–412.
- Holman RR, Paul SK, Bethel MA, et al. 10-year follow-up of intensive glucose control in type 2 diabetes. N Engl J Med. 2008;359:1577–1589.
- American Diabetes Association Professional Practice Committee. Standards of Care in Diabetes—2026, Sections 11 (Chronic Kidney Disease) and 12 (Retinopathy, Neuropathy, and Foot Care). Diabetes Care. 2026;49(Suppl 1).
- National Institute of Diabetes and Digestive and Kidney Diseases. Preventing Diabetes Problems.
This article is for general education and is not a substitute for advice from your own doctor, diabetes educator or pharmacist.