Do you need to fast for LH blood test?

LH blood test?

DefinitionThe LH blood test measures the amount of luteinizing hormone (LH). LH is a hormone released by the pituitary gland.In women, an increase in LH levels at mid-cycle causes ovulation.In men, LH stimulates production of testosterone.Alternative NamesICSH - blood test; Luteinizing hormone - blood test; Interstitial cell stimulating hormone - blood testHow the test is performedBlood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.How to prepare for the testThe health care provider may advise you to avoid drugs that may affect the test. Drugs that can decrease LH measurements include birth control pills, hormone replacement therapy, and testosterone.If you are a woman of childbearing age, the test may need to be done on a specific day of your menstrual cycle.How the test will feelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.Why the test is performedYour doctor may order this test if you are a woman who is having trouble getting pregnant, who does not have regular periods, or has signs of a disorder associated with abnormal levels of LH.Normal ValuesAdult female: 5 to 25 IU/L (levels peak around the middle of the menstrual cycle)Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.What abnormal results meanGreater-than-normal levels of LH may indicate:Anorchia(absence of testes or testes that do not function)HypogonadismKlinefelter syndromeMenopauseOvarian failure (see Ovarian hypofunction)Polycystic ovary diseasePrecocious pubertyTurner syndromeLower-than-normal levels of LH may indicate hypopituitarism.Additional conditions under which the test may be performed include:Anovulatory bleedingInfertilityMultiple endocrine neoplasia (MEN) IOvarian cystsWhat the risks areVeins and arteries vary in size from one patient 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.Other risks associated with having blood drawn are slight but may include:Excessive bleedingFainting or feeling light-headedHematoma (blood accumulating under the skin)Infection (a slight risk any time the skin is broken)Special considerationsRecent exposure to radioisotopes (a recent nuclear medicine scan, for example) can interfere with test results.ReferencesWebster RA. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders Elsevier; 2006:chap 25.Ferri FF. Laboratory tests and interpretation of results. In: Ferri FF, ed. Ferri's Clinical Advisor 2009. 1st ed. Philadelphia, Pa: Mosby Elsevier; 2009:section IV.