What Is a Blood Test? A blood test is when a sample of blood is taken from the body to be tested in a lab. Doctors order blood tests to check things such as the levels of glucose, hemoglobin, or white blood cells. This can help them detect problems like a disease or medical condition. Sometimes, blood tests can help them see how well an organ (such as the liver or kidneys) is working. What Is a Glucose Test? A glucose test measures how much glucose is in the blood. Glucose is a type of sugar used by the body for energy. Why Are Glucose Tests Done? A glucose test is done to check for low or high levels of glucose. Sometimes it's done as part of a routine checkup to screen for problems, and sometimes because a child has not been feeling well. A low glucose level is called hypoglycemia. A high level of glucose is called hyperglycemia. High glucose levels can point to diabetes. How Should We Prepare for a Glucose Test? Your child may be asked to stop eating and drinking for 8 to 12 hours before the test. Tell your doctor about any medicines your child takes because some drugs might affect the test results. Wearing a T-shirt or short-sleeved shirt for the test can make things easier for your child, and you also can bring along a toy or book as a distraction. How Is a Glucose Test Done? Most blood tests take a small amount of blood from a vein. To do that, a health professional will: clean the skin put an elastic band (tourniquet) above the area to get the veins to swell with blood insert a needle into a vein (usually in the arm inside of the elbow or on the back of the hand) pull the blood sample into a vial or syringe take off the elastic band and remove the needle from the vein In babies, blood draws are sometimes done as a "heel stick collection." After cleaning the area, the health professional will prick your baby's heel with a tiny needle (or lancet) to collect a small sample of blood. Glucose is sometimes tested with a "fingerstick" test. The health profession will clean your child's finger, then prick the tip of it with a tiny needle (or lancet) to collect the blood. Collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Can I Stay With My Child During a Glucose Test? Parents usually can stay with their child during a blood test. Encourage your child to relax and stay still because tensing muscles can make it harder to draw blood. Your child might want to look away when the needle is inserted and the blood is collected. Help your child to relax by taking slow deep breaths or singing a favorite song. How Long Does a Glucose Test Take? Most blood tests take just a few minutes. Occasionally, it can be hard to find a vein, so the health professional may need to try more than once. What Happens After a Glucose Test? The health professional will remove the elastic band and the needle and cover the area with cotton or a bandage to stop the bleeding. Afterward, there may be some mild bruising, which should go away in a few days. When Are Glucose Test Results Ready? Blood samples are processed by a machine, and it may take anywhere from a few minutes to a day for the results to be available. If the test results show signs of a problem, the doctor might order other tests to figure out what the problem is and how to treat it. Are There Any Risks From Glucose Tests? A glucose test is a safe procedure with minimal risks. Some kids might feel faint or lightheaded from the test. A few kids and teens have a strong fear of needles. If your child is anxious, talk with the doctor before the test about ways to make the procedure easier. A small bruise or mild soreness around the blood test site is common and can last for a few days. Get medical care for your child if the discomfort gets worse or lasts longer. If you have questions about the glucose test, speak with your doctor or the health professional doing the blood draw. Back to Articles Related Articles Definition: Blood Glucose Level Blood glucose level is the amount of glucose in the blood. Read More Definition: Hyperglycemia Hyperglycemia occurs when the level of glucose in the blood is higher than it should be. Read More Definition: Hypoglycemia Hypoglycemia occurs when the level of glucose in the blood is lower than it should be. Read More Blood Glucose Record If you have diabetes, you can use this printable sheet to record your blood glucose levels. Read More Diabetes Center Our Diabetes Center provides information and advice for teens about treating and living with diabetes. Read More What Is Gestational Diabetes? Find out what the experts have to say. Read More Getting a Blood Test (Video) A blood test might sound scary, but it usually takes less than a minute. Watch what happens in this video for kids. Read More Hypoglycemia When blood glucose levels drop too low, it's called hypoglycemia. Very low blood sugar levels can cause severe symptoms that require immediate treatment. Read More Monitoring Blood Sugar To keep blood sugar levels under control, you have to check them regularly. Learn about checking and recording your child's blood sugar levels. Read More Blood Test (Video) These videos show what's involved in getting a blood test and what it's like to be the person taking the blood sample. Read More Diabetes Center Diabetes means a problem with insulin, an important hormone in the body. Find out how children with diabetes can stay healthy and do the normal stuff kids like to do. Read More Helping Kids Deal With Injections and Blood Tests Blood tests and insulin injections can be a challenge for kids with diabetes and their parents. Here are some strategies for coping with these necessary procedures. Read More Blood Glucose Record If your child has diabetes, you can use this printable sheet to record his or her blood glucose levels. Read More Type 2 Diabetes: What Is It? Learning what you can about type 2 diabetes will let you help your child manage and live with the disease. Here are the basics. Read More Hyperglycemia and Diabetic Ketoacidosis When blood glucose levels (also called blood sugar levels) are too high, it's called hyperglycemia. A major goal in controlling diabetes is to keep blood sugar levels as close to the desired range as possible. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.