Testing your blood sugar at home—also called self-monitoring of blood glucose (SMBG)—is the single best tool you have to manage your type 1 or type 2 diabetes on a daily basis. Why? Testing helps you:

1. Catch and treat any dangerous blood sugar highs or lows.
2. Understand how your blood sugar rises in reaction to certain foods.
3. Recognize how exercise changes your blood sugar levels.
4. Determine if your diabetes medications are working.
5. Calculate your insulin dose for meals (if you have been prescribed a rapid-acting insulin).

By using the information from regular blood sugar testing, you can make sure your efforts to eat right, exercise, and take your medications are paying off. And studies show that keeping your blood sugar under control is the best way to reduce your risk of long-term diabetes complications like kidney damage and heart and eye disease.

What is a healthy blood sugar level?

Everyone has unique blood sugar targets based on their individual medical history, age, and lifestyle needs. However, the American Diabetes Association (ADA) recommends the following general goals for non-pregnant adults:

Fasting (before meals; upon waking): 70–130 mg/dL (3.9–7.2 mmol/L)

Postprandial (one to two hours after the start of a meal): no greater than 180 mg/dL (10.0 mmol/L)

Remember, these are only guidelines. Talk to your doctor or diabetes educator about the blood sugar targets that are right for you. They can also advise you on how often you should be testing.

What is a blood sugar emergency?

Extremely high or low blood sugars can be dangerous to people with type 1 or type 2 diabetes.

Insulin treatments and certain oral diabetes medications can trigger blood sugar lows, or hypoglycemia. Everyone has a different lower threshold for feeling the effects of hypoglycemia, but generally speaking, many people experience symptoms when their blood sugars drop below 70 mg/dL (3.9 mmol/L). Symptoms include shakiness, confusion, sweating, and clammy skin. When left untreated, hypoglycemia can be life-threatening, so detecting and treating low blood sugar immediately is important.

On the other end of the spectrum, when blood sugar reaches very high levels (over 600 mg/dL; 33.3 mmol/L), it can cause a life-threatening condition known as hyperosmolar hyperglycemic nonketotic syndrome (HHNS).

People with type 2 diabetes are at particular risk for hyperglycemia when they are sick or injured. It’s important to create a “Sick Day Plan” with your doctor before you are ill to prepare for these situations before they happen.

When should I call my doctor?

Generally speaking, if your blood sugars are over 240 mg/dL (13.3 mmol/L) for more than 24 hours, you should call your doctor for advice.

Occasional ups and downs in blood sugar control are normal. But if you are consistently having trouble keeping your blood sugars in your healthy target range, you should also talk to your doctor. Bring your blood sugar testing logs with you to discuss. By working together, you can troubleshoot the numbers and adjust your treatment plan.