What Is Normal Blood Sugar?

Medically reviewed by Kelly Wood, MD

Blood sugar (glucose) is the main type of sugar in your blood. You get it from the carbohydrates you consume. Glucose is the primary source of energy for your body’s cells, tissues, and organs.

Normal blood sugar is about 70-99 mg/dL. Your blood sugar will naturally fluctuate a bit throughout the day in response to food. However, it ideally stays within a set range and doesn’t change very much based on what you eat or your level of physical activity.

Monitoring your blood sugar can help prevent serious complications, including heart attack and kidney disease. It’s especially critical to monitor blood glucose if you have diabetes, a chronic condition that leads to excess glucose in the blood.

Normal Blood Sugar Levels

A number of factors can affect your blood sugar, including alcohol consumption, certain antibiotics, and the amount of insulin in your bloodstream. Insulin is a hormone that helps regulate blood glucose levels.

Normal blood sugar levels for people without diabetes, recommended target ranges for people with diabetes, can vary based on factors like:

• Age

• Level of physical activity

• Stress

• Illness

• Medications

The following chart includes general guidelines for blood sugar levels, measured in milligrams per deciliter (mg/dL).

How Is Blood Sugar Tested?

A healthcare provider may recommend one or more of the following tests to test your blood sugar. These tests can help diagnose prediabetes or diabetes. Prediabetes means your blood sugar is higher than normal, but not high enough to be diagnosed with diabetes.

Types of diabetes include:

• Type 1: An autoimmune condition in which your immune system mistakenly attacks insulin-producing cells, which turns off insulin production. Type 1 diabetes can’t be prevented.

• Type 2: A chronic condition in which your body doesn't make enough insulin or doesn't use it properly, leading to elevated blood sugar levels. Type 2 diabetes is preventable through lifestyle, including eating a nutritious diet and engaging in physical activity regularly.

• Gestational: High blood sugar during pregnancy that usually resolves after delivery.

An endocrinologist is a medical doctor who specializes in hormones. If you are diagnosed with diabetes or prediabetes, you’ll likely work with an endocrinologist. You'll also probably start monitoring your blood sugar levels throughout the day on an ongoing basis.

In-Office Testing

Testing your blood sugar is relatively simple and you won’t wait long for results. Possible tests you may receive in a healthcare provider’s office include the A1C, fasting plasma glucose (FPG), and an oral glucose tolerance test (OGTT).

AIC: This test is also known as the hemoglobin A1C or HbA1c test. Your healthcare provider will take a small sample of blood from your finger or arm. The test determines your average blood sugar levels over the past three months. It can be done right in the office or at a lab and doesn’t require any preparation.

FPG: This test measures your blood glucose levels after you’ve fasted for at least eight hours. You’ll need to avoid eating or drinking anything except water for eight hours before the test. It’s usually performed first thing in the morning.

OGTT: This test is often used to screen for gestational diabetes. You’ll eat a normal carbohydrate diet for the three days before testing, then fast for 10-16 hours. At your appointment, your healthcare provider will take a baseline sample of blood using a needle. You’ll drink glucose after that. You may be tested again after 30 minutes, 60 minutes, 90 minutes, or 120 minutes to see how your body reacts to the glucose. There are multiple variations of this test, including different glucose doses and sampling intervals.

Related: How Is Type 2 Diabetes Treated?

At-Home Testing

You can use a small, portable device called a blood sugar meter (glucometer) to monitor your blood sugar at home. There are many kinds of meters, or monitors, and you can buy them in a variety of places, including online and at your nearest pharmacy. They often work the same way and include a lancing (pricking) device called a lancet. You’ll need to buy more lancets, as well as test strips, so you have a supply.

Here are the steps to monitor your blood sugar using your glucometer:

1. Make sure the machine is clean.

2. Remove one test strip from the package and close the package immediately. Water can damage the strips.

3. Wash your hands with soap and dry them well. Gently massage the finger you’ll use for the test to increase blood flow to that area.

4. Use a lancet to prick your finger.

5. Squeeze a bit of blood onto the test strip or hold the edge of the test strip to the drop of blood.

6. Place the test strip in the meter and wait for the results. Results appear after a few seconds.

7. Throw away the lancet and test strip.

You can keep track of your results using a phone app or on a piece of paper that you’ll bring to appointments with your healthcare provider. Tracking will likely include your blood glucose level before meals as well as 1-2 hours after meals.

Do not share lancets with anyone else, and make sure that someone you know—for example, someone you live with—knows how to use your glucometer so they can monitor your blood sugar if you’re sick.

Who Might Need a Blood Sugar Test?

Your healthcare provider may perform a blood sugar test if you:

• Have symptoms of high or low blood sugar

• Are at an increased risk of developing diabetes

• Are pregnant

You will discuss next steps based on your results. Next steps might include additional tests, medication, and lifestyle changes. They may recommend monitoring your blood glucose levels regularly, especially if you:

• Take insulin

• Have difficulty reaching your target glucose range

• Have low blood sugar levels with or without the usual signs

• Are pregnant

Abnormal Blood Sugar

High blood sugar (hyperglycemia) is a fasting blood glucose level between 100 and 125 mg/dL. This indicates prediabetes. Anything over 125 mg/dL qualifies as diabetes and can increase your risk of heart disease or stroke.

Low blood sugar (hypoglycemia) is a fasting blood sugar below 70 mg/dL. Severely low blood glucose levels (below 54 mg/dL) can increase your risk of complications like fainting and seizures.

High Blood Sugar

Hyperglycemia can occur with or without diabetes. For example, it can be caused by stress or illness.

Many things can spike blood sugar in people who have diabetes. For example, you may not have given yourself enough insulin, you may not use insulin effectively (insulin resistance), or you may not be getting enough physical activity to support your health.

Other potential triggers include:

• Sunburns

• Artificial sweeteners

• Coffee

• Lack of sleep

• Skipping breakfast

• Dehydration

• Nasal sprays

• Gum disease

Common signs you may have high blood sugar include:

• Vision problems

• Extreme thirst or dry mouth

• Dry skin

• Feeling weak or tired

• Frequent urination (polyuria)

Treatment for hyperglycemia depends on your blood sugar level. For example, exercise can lower your blood glucose level for up to 24 hours, depending on your insulin sensitivity.

However, if your blood sugar is above 240 mg/dL, your urine may contain ketones. Ketones are acids produced when your body breaks down fat for energy because there’s not enough glucose available. Exercising requires energy, which means your body will produce more ketones. High levels of ketones can lead to an emergency medical condition called diabetic ketoacidosis (DKA).

Reaching out to your healthcare provider is the most effective way to prevent complications from high blood sugar. They may alter your medication or insulin dosage or refer you to a registered dietitian (RD). An RD is a healthcare professional who has specific training on diet and nutrition. They can help you create a meal plan that helps keep your blood glucose level stable.

Low Blood Sugar

Hypoglycemia can also occur with or without diabetes.

Causes of low blood sugar include:

• Certain types of diabetes medications and other drugs

• Alcohol consumption

• Insulinoma (a rare tumor in the pancreas)

• Lacking a hormone like cortisol, growth hormone, or thyroid hormone

• Heart, kidney, or liver failure

• Previous weight-loss surgeries

You might not exhibit any signs of low blood sugar, but they can include:

• Vision problems

• Fast heart rate

• Sweating

• Headaches

• Fatigue

• Crankiness

• Tingling or numbness

• Difficulty thinking clearly

Low blood sugar can be dangerous, but it’s treatable. You can follow the “15-15 rule” if your glucose level dips to 55 and 69 mg/dL: Eat 15 grams of low-fiber, low-fat carbohydrates and repeat every 15 minutes until your blood sugar is over 70 mg/dL. Fiber and fat slow down digestion, so foods like beans or chocolate won’t help restore blood sugar levels quickly.

Carbohydrate choices include:

• 4 ounces (oz) of juice

• 1 tablespoon of sugar, honey, or maple syrup

• 6-7 hard candies

• 3 glucose tablets (chewable sugar tablets)

Young children usually require fewer carbohydrates, so ask their doctor how much they need.

Call 911 if your blood sugar is below 55 mg/dL, and use an injectable glucagon (an emergency medication) at home if you have a kit.

A Quick Review

Blood sugar, or glucose, is the main type of sugar in your blood. It acts like fuel for your body and comes from the foods you eat.

It’s important to maintain healthy levels of blood sugar, especially if you have diabetes. Reach out to a healthcare provider if you experience symptoms that might indicate high or low blood sugar. You might be at risk for a number of complications if it’s left untreated.

Testing your blood glucose level is quick and simple. You can do it at home or at a healthcare provider’s office, and you’ll have your results immediately.

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