Obtaining a blood sample from some people may be more difficult than from others. ElSayed NA, Aleppo G, Aroda VR, et al. Classification and diagnosis of diabetes: standards of care in diabetes Diabetes Care. PMID: pubmed. US Preventive Services Task Force; Davidson KW, Barry MJ, Mangione CM, et al.

Screening for prediabetes and type 2 diabetes: US Preventive Services Task Force recommendation statement. Reviewed by: Sandeep K.

Dhaliwal, MD, board-certified in Diabetes, Endocrinology, and Metabolism, Springfield, VA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A. Editorial team. Share Facebook Twitter Linkedin Email Home Health Library. Blood sugar test - blood Random blood sugar; Blood sugar level; Fasting blood sugar; Glucose test; Diabetic screening - blood sugar test; Diabetes - blood sugar test.

How the Test is Performed A blood sample is needed. How to Prepare for the Test The test may be done in the following ways: After you have not eaten anything for at least 8 hours fasting At any time of the day random Two hours after you drink a certain amount of glucose oral glucose tolerance test.

How the Test will Feel When the needle is inserted to draw blood, some people feel moderate pain. Why the Test is Performed Your health care provider may order this test if you have signs of diabetes.

The blood glucose test is also used to monitor people who already have diabetes. The test may also be done if you have: An increase in how often you need to urinate Recently gained a lot of weight Blurred vision Confusion or a change in the way you normally talk or behave Fainting spells Seizures for the first time Unconsciousness or coma SCREENING FOR DIABETES This test may also be used to screen a person for diabetes.

This increases your risk of developing type 2 diabetes and you should consult with your provider. Your provider will order a fasting blood glucose, A1C test , or glucose tolerance test , depending on your random blood glucose test result. In someone who has diabetes, an abnormal result on the random blood glucose test may mean that the diabetes is not well controlled.

Talk with your provider about your blood glucose goals if you have diabetes. Other medical problems can also cause a higher-than-normal blood glucose level, including: Overactive thyroid gland Pancreatic cancer Swelling and inflammation of the pancreas pancreatitis Stress due to trauma, stroke, heart attack, or surgery Rare tumors, including pheochromocytoma , acromegaly , Cushing syndrome , or glucagonoma A lower-than-normal blood glucose level hypoglycemia may be due to: Hypopituitarism a pituitary gland disorder Underactive thyroid gland or adrenal gland Tumor in the pancreas insulinoma - very rare Too little food Too much insulin or other diabetes medicines Liver or kidney disease Weight loss after weight loss surgery Vigorous exercise Some medicines can raise or lower your blood glucose level.

Risks There is little risk involved with having your blood taken. Other risks associated with having blood drawn are slight, but may include: Excessive bleeding Fainting or feeling lightheaded Multiple punctures to locate veins Hematoma blood accumulating under the skin Infection a slight risk any time the skin is broken.

References ElSayed NA, Aleppo G, Aroda VR, et al. Find a Doctor Request an Appointment. close ×. This measures your blood sugar before and after you drink a liquid that contains glucose.

Source: American Diabetes Association. If your doctor thinks you have type 1 diabetes, your blood may also tested for autoantibodies substances that indicate your body is attacking itself that are often present in type 1 diabetes but not in type 2 diabetes.

You may have your urine tested for ketones produced when your body burns fat for energy , which also indicate type 1 diabetes instead of type 2 diabetes. Gestational diabetes is diagnosed using blood tests.

If your risk is higher for getting gestational diabetes due to having more risk factors , your doctor may test you earlier. Results can differ depending on the size of the glucose drink and how often your blood sugar is tested. Ask your doctor what your test results mean.

If your test results show you have prediabetes, ask your doctor or nurse if the lifestyle change program offered through the CDC-led National Diabetes Prevention Program is available in your community.

You can also search for an online or in-person program. If your test results show you have type 1, type 2, or gestational diabetes, talk with your doctor or nurse about a detailed treatment plan—including diabetes self-management education and support services —and specific steps you can take to be your healthiest.

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Under standardized meal conditions with a moderately low percentage carbohydrate 50 grams, The mean BMI of these participants was overweight, at Their results found:. Taking into account additional research performed specifically using continuous glucose monitors, we can gain some more clarity on normal trends and can suggest that a nondiabetic, healthy individual can expect:.

These are not standardized criteria or ranges but can serve as a simple guide for what has been observed as normal in people without diabetes. Many people may likely do better at lower post-meal glucose levels.

Lastly, there are no specific recommendations regarding the average glucose levels over 24 hours using CGMs. This lack of standardization is likely because CGMs are relatively new and not widely used in a nondiabetic population. The following is a summary of insights from our review of the research.

You should consult your doctor before setting glucose targets or changing dietary and lifestyle habits. However, multiple research studies show that as fasting glucose increases, there is an increased risk of health problems like diabetes and heart disease — even if it stays within the normal range.

The highlights of some of the study results include:. In a study looking at healthy, young, adults without diabetes who had normal BMI mean of In a study looking at healthy adults without diabetes, researchers found that the average post-meal glucose peak was 99 ± These numbers represent the mean hour glucose range in a young, very healthy population.

We looked at several studies of people without diabetes wearing CGMs, and this was one of the overall healthiest populations under normal living conditions. It is common for your glucose levels to increase after a meal: you just ate food that may contain glucose, and now your body is working on getting it out of the bloodstream and into the cells.

Spikes are also associated with heart disease. Repeated high glucose spikes after meals contribute to inflammation, blood vessel damage , increased risk of diabetes, and weight gain. Additionally, the data shows that the big spikes and dips in glucose are more damaging to tissues than elevated but stable glucose levels.

Therefore, you should strive to keep your glucose levels as steady as possible, at a low and healthy baseline level, with minimal variability after meals. Each person has an individual response to food when it comes to their glucose levels; studies have shown that two people can have different changes in their glucose levels after eating identical foods.

The difference can be pretty dramatic. One study found that some people had equal and opposite post-meal glucose spikes in response to the same food. So, how do you keep your glucose levels stable? How do you know when you have a sugar spike and which foods cause it? Continuous glucose monitoring allows you to see your blood glucose levels in real time and store that data for future reference; this makes CGMs uniquely positioned to help you optimize your diet and lifestyle.

Foods affect each person differently, and it is hard to know what your blood glucose is doing at any one time without measuring it. CGMs can give you the data you need to optimize your health.

Choosing foods and lifestyle habits that consistently keep average glucose lower and post-meal spikes lower will improve glucose patterns over time. Studies have shown that the information gathered from CGMs can provide more detail and potential areas for modification than the single glucose level you get with a glucometer or laboratory blood test.

CGMs can not only give you data on your blood glucose, but they can help you use the data to make changes to your diet and exercise routines. This technology can allow people to create personalized meal plans that suit their unique metabolic needs and improve glucose control.

Why is it unhealthy for glucose levels to be too high hyperglycemia or too low hypoglycemia? Hyperglycemia refers to elevated blood glucose levels. This usually occurs because the body does not appropriately remove glucose from the blood; this can happen due to many complex reasons.

Elevated glucose levels can damage blood vessels and nerves over time; this can then lead to problems in the eyes, kidneys, and heart, as well as numbness in the hands and feet. Very high levels can lead to coma and even death in some cases. If your doctor determines that your blood glucose blood sugar level is very high, or if you have classic symptoms of high blood glucose in addition to one positive test, your doctor may not require a second test to diagnose diabetes.

The A1C test measures your average blood glucose for the past two to three months. The advantages of being diagnosed this way are that you don't have to fast or drink anything.

This test checks your fasting blood glucose levels. Fasting means after not having anything to eat or drink except water for at least 8 hours before the test.

This test is usually done first thing in the morning, before breakfast. The OGTT is a two-hour test that checks your blood glucose levels before and two hours after you drink a special sweet drink.

If you're overweight and have any of the other risk factors below, ask your provider about getting tested at an earlier age and more often:. Children age 10 and older who are overweight and have at least two of the risk factors listed above should be tested for type 2 diabetes every 3 years, even if they have no symptoms.

If you had a random blood glucose test, a normal result depends on when you last ate. The examples above show the common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories.

Some labs use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results. Blood glucose measured by a blood test from a vein is considered more accurate than blood glucose measured from a fingerstick with a blood glucose meter, or blood glucose measured by a continuous glucose monitor.

A lower-than-normal blood glucose level hypoglycemia may be due to:. Some medicines can raise or lower your blood glucose level. Before having the test, tell your provider about all the medicines you are taking. There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other.

Obtaining a blood sample from some people may be more difficult than from others. ElSayed NA, Aleppo G, Aroda VR, et al.

Classification and diagnosis of diabetes: standards of care in diabetes Diabetes Care. PMID: pubmed. US Preventive Services Task Force; Davidson KW, Barry MJ, Mangione CM, et al.

Screening for prediabetes and type 2 diabetes: US Preventive Services Task Force recommendation statement.