Blood Glucose: Targets, Testing, and the Signs of Highs and Lows

Blood glucose, or blood sugar, is the main sugar in your blood and your body’s primary source of energy. It comes from food: your body breaks most of what you eat down into glucose and releases it into the bloodstream. Rising glucose signals the pancreas to release insulin, a hormone that helps glucose get into your cells to be used for energy.

When glucose runs too high: diabetes

In diabetes, blood glucose is too high because the body doesn’t make enough insulin, can’t use it as well as it should, or both. Glucose stays in the blood instead of reaching the cells, and over time the excess can cause serious complications. That’s why people with diabetes try to keep their glucose within a target range.

Typical targets

Your own targets may differ with your age, other health problems and other factors — ask your health care team what range is right for you.

Checking your glucose

• Every day, or more. Most people with diabetes check daily; some need to check several times a day.
• Blood glucose meter — the most common home method, testing a small drop of blood, usually from a fingertip.
• Continuous glucose monitoring (CGM) — a tiny sensor under the skin measures glucose every few minutes, day and night. It is especially useful for people who take insulin and have trouble with low blood sugar.
• A1C — a blood test your provider uses to measure your average glucose over the past three months, usually at least twice a year, and more often if you aren’t meeting treatment goals.

Too high: hyperglycemia

Signs your glucose may be too high:

• feeling thirsty
• feeling tired or weak
• headaches
• urinating often
• blurred vision

If you often run high or have these symptoms, talk to your health care team; you may need changes to your meal plan, activity or medicines. High glucose can also come from other conditions affecting insulin or glucose, such as problems with the pancreas or adrenal glands.

Too low: hypoglycemia

Hypoglycemia means glucose has dropped below what is healthy for you — for many people with diabetes, a reading under 70 mg/dL, though your number may differ. Symptoms tend to come on quickly and vary from person to person:

• shaking and sweating
• nervousness or anxiety
• irritability or confusion
• dizziness
• hunger

Low glucose is common in type 1 diabetes and in type 2 diabetes treated with certain medicines. If you think your glucose may be low, check it even without symptoms — low blood sugar can be dangerous and should be treated right away.

Rarely, people without diabetes get low blood sugar, from conditions such as liver or kidney disease or hormone deficiencies, or from some medicines, including certain heart drugs and antibiotics. A provider can find the cause and the treatment.

Sources

Based on "Blood Glucose," MedlinePlus, U.S. National Library of Medicine, drawing on the National Institute of Diabetes and Digestive and Kidney Diseases; a work of the United States government in the public domain.