Blood Sugar & Diabetes
Blood Sugar & Diabetes: A Plain-English Guide
High blood sugar often develops quietly, over years, without obvious symptoms. This guide explains what blood sugar is, how prediabetes and diabetes are diagnosed, what the test numbers mean, and which everyday habits can make a real difference.
Last updated: September 23, 2026 ยท Based on guidance from the CDC and the National Institutes of Health (NIDDK)
Key takeaways
- Prediabetes is common and often silent. It means blood sugar is higher than normal but not yet in the diabetes range, and many people have no symptoms.
- Know the numbers. A normal A1C is below 5.7%. An A1C of 5.7% to 6.4% is in the prediabetes range, and 6.5% or higher is in the diabetes range. Only a healthcare provider can make a diagnosis.
- Lifestyle matters. The NIH notes that changes such as losing weight and being active most days may help prevent or delay type 2 diabetes.
- Be careful with medications and supplements. Never stop or change diabetes medication, or add a supplement, without talking to your provider.
What is blood sugar?
Blood sugar (blood glucose) is the main source of energy for your body’s cells. It comes mostly from the carbohydrates you eat. After a meal, your pancreas releases a hormone called insulin, which helps glucose move out of your bloodstream and into your cells.
Problems start when the body doesn’t make enough insulin or when cells stop responding to it well, a condition called insulin resistance. Glucose then builds up in the blood. Over time, consistently high blood sugar can damage blood vessels and nerves and affect the heart, kidneys, eyes and feet.
Types of diabetes
- Type 1 diabetes: The immune system attacks the insulin-producing cells in the pancreas, so the body makes little or no insulin. People with type 1 diabetes need insulin. It is not caused by lifestyle.
- Type 2 diabetes: The most common type. The body doesn’t use insulin well and may not make enough. Risk is linked to excess weight, physical inactivity, family history and age.
- Prediabetes: Blood sugar is above normal but below the diabetes range. It raises the risk of developing type 2 diabetes, but it can often be improved.
- Gestational diabetes: Diabetes that develops during pregnancy. It usually goes away after delivery but raises the risk of type 2 diabetes later in life.
How blood sugar is tested
According to the CDC, the main tests are:
- A1C test: shows your average blood sugar over roughly the past 2 to 3 months. No fasting needed.
- Fasting plasma glucose: measures blood sugar after an overnight fast.
- Oral glucose tolerance test: measures blood sugar before and after you drink a sugary liquid.
- Random plasma glucose: measures blood sugar at any time of day.
Here’s how A1C and fasting results are commonly interpreted:
| Result | A1C | Fasting plasma glucose |
|---|---|---|
| Normal | Below 5.7% | Below 100 mg/dL |
| Prediabetes | 5.7% to 6.4% | 100 to 125 mg/dL |
| Diabetes | 6.5% or higher | 126 mg/dL or higher |
A diagnosis is usually confirmed with repeat testing. The NIDDK also notes that some conditions can make A1C results inaccurate, including iron-deficiency anemia, recent blood loss, kidney failure and liver disease. Always review your results with your healthcare provider.
Who should get tested?
If you have risk factors for prediabetes or type 2 diabetes, talk with your healthcare provider about testing. Common risk factors include:
- Having overweight or obesity
- Being physically inactive
- Having a parent or sibling with type 2 diabetes
- Being older, since risk rises with age
- Having had gestational diabetes
According to the NIDDK, even if your results are normal, people at higher risk should be retested at least every 3 years.
Symptoms of high blood sugar
Prediabetes usually causes no clear symptoms, which is why testing matters. When blood sugar is high, people may notice:
- Urinating often, especially at night
- Feeling very thirsty
- Blurry vision
- Feeling unusually tired
- Cuts or sores that heal slowly
- Losing weight without trying
If you notice these symptoms, see a healthcare provider promptly. Seek emergency care for severe symptoms such as confusion, vomiting, trouble breathing, or extreme drowsiness.
Everyday habits that support healthy blood sugar
The NIDDK notes that lifestyle changes such as losing weight and being physically active most days of the week may help prevent or delay type 2 diabetes. Practical habits include:
- Reaching a healthier weight. Even modest weight loss can help. See our guide to healthy weight loss for realistic, evidence-based steps.
- Moving regularly. Physical activity helps your muscles use glucose and can improve how your body responds to insulin.
- Building balanced meals. Pair carbohydrates with fiber, protein and healthy fats, and favor whole grains, vegetables and beans over refined starches.
- Cutting back on sugary drinks. Sodas and sweetened drinks can raise blood sugar quickly.
- Sleeping well and not smoking. Both affect overall metabolic health.
- Keeping up with checkups. Regular testing helps you and your provider catch changes early.
What about blood sugar supplements?
Many supplements are marketed for blood sugar support, often built around ingredients such as chromium, cinnamon, berberine or gymnema. Research on these ingredients ranges from promising to mixed to weak, and results depend on the ingredient, the dose and the person.
Keep these points in mind:
- Supplements are not a substitute for diabetes treatment. They can’t diagnose, treat or cure diabetes.
- Interactions are a real risk. Some ingredients may lower blood sugar. Combined with diabetes medication, that could push blood sugar too low (hypoglycemia).
- Talk to your provider or pharmacist first, especially if you take insulin or other glucose-lowering medication.
We’ll be publishing ingredient-by-ingredient research that separates solid evidence from marketing claims, and we’ll link it here.
Blood sugar and your teeth
Diabetes affects more than blood sugar. The National Institute of Dental and Craniofacial Research notes that people with conditions such as diabetes may be at higher risk for gum disease, and their dentist may want to see them more often. Learn the daily habits that protect your gums in our dental health guide.
Related guides
- Healthy Weight Loss: What Actually Works. Realistic steps for reaching and keeping a healthier weight.
- Dental Health Basics. How to protect your teeth and gums, which is especially important if you have diabetes.
Sources
- Centers for Disease Control and Prevention. Diabetes Testing.
- Centers for Disease Control and Prevention. Prediabetes (Diabetes Report Card).
- National Institute of Diabetes and Digestive and Kidney Diseases. The A1C Test & Diabetes.
- National Institute of Dental and Craniofacial Research. Oral Hygiene.
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. If you have or think you may have diabetes, work with a qualified healthcare provider.
Our blood sugar supplement reviews
Read our ingredient-by-ingredient reviews before you buy any blood sugar supplement. Always check with your doctor first if you take diabetes medication.