What It Is An estradiol test measures the level of the hormone estradiol in the bloodstream. Estradiol plays an important role in sexual development: It's the most important form of the hormone estrogen. In sexually mature females, it's produced mainly by the ovaries, and in smaller amounts by the adrenal glands. Estrogen is also produced by the placenta during pregnancy. Sexually mature males have much lower blood levels of estradiol, which are produced by the testes and adrenal glands. In young girls, estradiol levels are normally low. As puberty approaches, usually between ages 8 and 14, the pituitary gland, located just beneath the brain, secretes two hormones (luteinizing hormone, or LH; and follicle-stimulating hormone, or FSH) that work together to stimulate the ovaries to make estradiol. Increased estradiol production is largely responsible for breast development, genital growth, and changes in the distribution of body fat in pubescent girls. Because human sex hormones work so closely with one another, doctors often perform the estradiol test with tests for LH, FSH, testosterone (the male sex hormone — but teen and adult females produce some, too), and progesterone (the hormone that prepares the body for pregnancy). Taken together, the results can often provide a more complete picture of a person's sexual maturation status and help doctors diagnose diseases causing sex hormone imbalances. Why It's Done Doctors may order an estradiol test if a girl appears to be entering puberty earlier or later than expected. High levels are associated with precocious (early) puberty, while low levels may indicate a delay in sexual development. Estradiol levels also give important information on the functioning of the ovaries. This can help doctors evaluate menstrual problems, including abnormal bleeding or missing periods. The test may also be used in boys or girls to check for damage or disease of the testes, ovaries, or adrenal glands. Testing estradiol levels also can be used to monitor the progression of a pregnancy, fertility treatments, or to evaluate menopause symptoms. Preparation No special preparations are needed for this test. On the day of the test, having your child wear a T-shirt or short-sleeved shirt can make things easier for your child and the technician who will be drawing the blood. The Procedure A health professional will usually draw the blood from a vein. First, the skin surface is cleaned with antiseptic, and an elastic band (tourniquet) is placed around the upper arm to apply pressure and cause the vein to swell with blood. Then, a needle is inserted into a vein (usually in the arm inside of the elbow or on the back of the hand) and blood is withdrawn and collected in a vial or syringe. After the procedure, the elastic band is removed. Once the blood has been collected, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding. Collecting the blood for the test will only take a few minutes. What to Expect Collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Afterward, there may be some mild bruising, which should go away in a few days. Getting the Results The blood sample will be processed by a machine. The results usually are available within a few days. Risks The estradiol blood test is considered a safe procedure. However, as with many medical tests, some problems can occur with having blood drawn, such as: fainting or feeling lightheaded hematoma (blood accumulating under the skin causing a lump or bruise) pain associated with multiple punctures to locate a vein Helping Your Child Having a blood test is relatively painless. Still, many kids are afraid of needles. Explaining the test in terms your child can understand might help ease some of the fear. Allow your child to ask the technician any questions he or she might have. Tell your child to try to relax and stay still during the procedure, as tensing muscles and moving can make it harder and more painful to draw blood. It also may help for your child to look away when the needle is being inserted into the skin. If You Have Questions If you have questions about the estradiol test, speak with your doctor. Back to Articles Related Articles 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 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 Blood Test: Testosterone A testosterone blood test may be done if a boy appears to be entering puberty earlier or later than expected, or to check for damage or disease of the testes or ovaries, adrenal glands, or pituitary glands. Read More Blood Test: Luteinizing Hormone (LH) A luteinizing hormone (LH) test measures the level of this hormone in the bloodstream. LH plays an important role in sexual development. Read More Blood Test: Follicle Stimulating Hormone (FSH) Follicle stimulating hormone (FSH) plays an important role in sexual development. An FSH test to measure the level of FSH in the bloodstream may be done if a boy or girl appears to be entering puberty earlier or later than expected. Read More Precocious Puberty Precocious puberty - when signs of puberty start before age 7 or 8 in girls and age 9 for boys - can be tough for kids. But it can be treated. Read More Understanding Puberty Puberty was awkward enough when you were the one going through it. So how can you help your kids through all the changes? Read More Endocrine System The glands of the endocrine system and the hormones they release affect almost every cell, organ, and function of our bodies. 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.