Glucose is a simple sugar that supplies energy to cells throughout the body. Doctors often use glucose tests to help diagnose diabetes or prediabetes.
Blood glucose tests are usually done at a doctor’s office or pathology collection center. They can be performed by a phlebotomist, or you can perform them yourself with a glucose meter, test strip, and lancet.
What is glucose?
Glucose is a sugar and the body’s main source of energy. It comes from the food you eat, especially carbohydrates like bread, potatoes, and fruit. As food passes through your digestive system, acids and enzymes break it down into glucose. Then, your bloodstream carries it to the cells to use for energy. A hormone called insulin helps control how much glucose is in your bloodstream. High levels of glucose in the blood are a sign of diabetes, which can cause serious, long-term health problems.
Your blood sugar level changes throughout the day. It’s lowest first thing in the morning and after a fast and highest during and after meals. It can also be influenced by certain things, such as the time of the day (blood sugar tends to be lower in the evening), medications you take, nose sprays, and stress.
The glucose test is most commonly used to diagnose prediabetes, type 1 and type 2 diabetes, and gestational diabetes. It can also help monitor your treatment for these conditions. Your doctor may recommend that you monitor your blood sugar yourself using a home glucose testing or monitoring device.
You can use blood, urine, or saliva samples for the glucose test. A blood test is most common and requires a needle to draw your sample. Some people feel nothing, while others might experience a slight sting or prick that quickly disappears. You can also use a glucose meter to measure your blood sugar, which requires you to prick your finger with a lancet and then place a drop of blood on a test strip.
A urine and saliva test are less accurate ways to measure your glucose. A urinalysis involves drawing a sample of your urine with a special kit that contains a small sponge. A small speculum is then inserted into the sponge, and your sample is sent to a lab for analysis. A hemoglobin A1c (HbA1c) test can also be done, which measures your average blood sugar over the past 2-3 months. This is done by measuring the percentage of hemoglobin that has glucose attached.
How does a glucose test work?
A glucose test measures the amount of sugar called glucose in a sample of your blood. Glucose is a major source of energy for most cells, including your brain. Glucose comes from foods such as fruit, milk, bread, and pasta. The hormone insulin made by your body helps control the amount of glucose in your blood. If you have high blood sugar (hyperglycemia), it may be a sign of diabetes.
Your healthcare provider will ask you to prick your finger with a small needle (a lancet) to draw a blood sample. Then they will put the blood on a strip that’s inserted into a machine called a glucometer. The machine reads the blood glucose level and gives a result within seconds. A healthcare professional will place a bandage over the fingertip where the blood was drawn. There’s little risk associated with a glucose test, except that you might have moderate pain or slight bruising where the needle was inserted into your finger.
In some cases, your doctor may order a random blood sugar test. This test checks your blood glucose level at a time when you’re not eating or drinking anything except water. A normal fasting glucose level is less than 140 mg/dL (7.8 mmol/L).
If you have diabetes, your provider will also probably want to order a glucose tolerance test or an A1c test to see how well your diabetes is being controlled. These tests check your average blood glucose level over three months or more.
All pregnant women are offered a glucose screening test between 24 and 28 weeks gestation to look for gestational diabetes (GD). To do this, you will drink a liquid that contains 50 grams of glucose (a type of sugar). A phlebotomist will take a blood sample from your arm 60 minutes (one hour) after you finish drinking the glucose solution.
You should not eat anything but water for about eight hours before your test. Some medicines can raise or lower your blood glucose level, so tell your doctor about any medicines you’re taking.
What are the risks of a glucose test?
A glucose test is a type of blood test that measures the amount of sugar in the body. It is used to diagnose and monitor diabetes. It can also be used to determine if someone is at risk for developing diabetes or if they are experiencing symptoms of high blood sugar (hyperglycemia). Glucose tests are generally taken at a pathology collection center. They are typically performed in the morning, and you must fast up to eight hours before the test. The blood sample is usually taken from a vein in the arm.
Glucose is the body’s main energy source and fuels every cell in the body. It comes from the foods and drinks people consume and from breaking down stored forms of carbohydrates like glycogen. Blood glucose levels are normally controlled by a hormone called insulin. However, if a person has diabetes, their insulin levels are too low or do not work properly, which can lead to elevated blood glucose levels. High blood glucose can cause many complications, such as nerve and kidney damage.
People who are at risk for diabetes may need regular screenings, including glucose tolerance tests. Screenings can detect diabetes in its early stages when it is easier to treat and prevent complications. It is recommended that people are tested for diabetes at least once per year.
The glucose tolerance test measures how the body reacts to a large amount of sugar. It can help to determine if a person’s elevated blood sugar levels are due to diabetes, prediabetes, or gestational diabetes. During the test, a person is asked to drink a glucose solution that tastes similar to cola or orange juice. Blood samples are then taken before and after the glucose solution to see how the body responds.
There is little to no risk associated with a glucose test, although there are some risks associated with having a blood sample drawn or a finger prick. Some people can experience tenderness or a small bruise at the needle insertion site, which will usually resolve quickly.
What are the results of a glucose test?
If the glucose level is high, it’s a sign of diabetes. Over time, this can damage your eyes, kidneys, nerves, and blood vessels. It also puts you at higher risk of heart disease and stroke. A doctor can diagnose diabetes using a simple blood test. People with diabetes often use a blood sugar monitor at home to check their blood glucose levels.
The results of the glucose tolerance test are measured in milligrams per deciliter or millimoles per liter (mg/dL or mmol/L). Different labs have different normal value ranges. You should talk to your provider about the meaning of your specific test results.
You should fast for eight hours before a glucose tolerance test to get the most accurate results. You can drink water during this time but shouldn’t eat anything else. You should also tell your doctor about any medicines you are taking. Some medicines can affect the results of a glucose tolerance test.
A glucose challenge test is sometimes used during pregnancy to screen for gestational diabetes. This test is done between the 24th and 28th week of pregnancy. You will be asked not to eat or drink anything but water for 8 hours before the test. Then, you will be given a solution to drink that contains sugar. Blood will be tested every 30 to 60 minutes after you drink the solution.
If two or more of the readings are high, you have gestational diabetes. A third or more high reading means that you have type 2 diabetes.
In addition to a glucose tolerance test, your doctor may order a random plasma glucose test or an A1C blood test. The A1C test measures the amount of glucose in your blood over a period of three months. It better measures your average blood glucose level than a single blood sample.
If you’re pregnant, your doctor may also order a glucose tolerance test in the 34th week of your pregnancy to find out whether you have gestational diabetes. A glucose tolerance test in pregnancy can help prevent serious complications like miscarriage and premature birth.