BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuTBG blood testSerum thyroxine binding globulin; TBG level; Serum TBG level; Hypothyroidism - TBG; Hyperthyroidism - TBG; Underactive thyroid - TBG; Overactive thyroid - TBG thyroid hormone binding globulinThe TBG blood test measures the level of a protein that moves thyroid hormone throughout your body. This protein is called thyroxine-binding globulin (TBG). How the Test is Performed A blood sample is taken and then sent to a laboratory for testing.Blood sampleVenipuncture is the collection of blood from a vein. It is most often done for laboratory testing.ImageRead Article Now Book Mark Article How to Prepare for the Test Certain drugs and medicines can affect test results. Your health care provider may tell you to stop taking a certain medicine for a short time before the test. Never stop taking any medicine without first talking to your provider.These medicines and drugs can increase TBG level:Estrogens, found in birth control pills and estrogen replacement therapy Heroin Methadone and opioids Phenothiazines (certain antipsychotic drugs)The following medicines can decrease TBG levels: Depakote or depakene (also called valproic acid) Dilantin (also called phenytoin) and carbamazepine High doses of salicylates, including aspirin Male hormones, including androgens and testosterone Prednisone or other glucocorticoids (steroids) How the Test will Feel When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away. Why the Test is Performed This test may be done to diagnose problems with your thyroid. Normal Results Normal range is 13 to 39 micrograms per deciliter (mcg/dL), or 150 to 360 nanomoles per liter (nmol/L).Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results. What Abnormal Results Mean An increased TBG level may be due to:Acute intermittent porphyria (a rare metabolic disorder) Acute intermittent porphyriaPorphyrias are a group of rare inherited disorders. An important part of hemoglobin, called heme, is not made properly. Hemoglobin is a protein in ...ImageRead Article Now Book Mark Article Hypothyroidism (underactive thyroid) Liver disease, such as hepatitis Liver diseaseThe term "liver disease" applies to many conditions that stop the liver from working or prevent it from functioning well. Abdominal pain or swelling...ImageRead Article Now Book Mark Article Pregnancy (TBG levels normally increased during pregnancy) Note: TBG levels are normally high in newborns.Decreased TBG levels may be due to:Acute illness AcuteAcute means sudden. Acute symptoms appear, change, or worsen rapidly. It is the opposite of chronic.ImageRead Article Now Book Mark Article Acromegaly (disorder caused by too much growth hormone) AcromegalyAcromegaly is a condition in which there is too much growth hormone (GH) in your body.ImageRead Article Now Book Mark Article Hyperthyroidism (overactive thyroid) HyperthyroidismHyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive thyroid.ImageRead Article Now Book Mark Article Malnutrition Nephrotic syndrome (symptoms that show kidney damage is present) Nephrotic syndromeNephrotic syndrome is a group of symptoms and abnormal test results that include protein in the urine, low blood protein levels in the blood, high ch...ImageRead Article Now Book Mark Article Stress from surgery High or low TBG levels affect the relationship between total T4 and free T4 blood tests. A change in TBG blood levels can alter the appropriate dose of levothyroxine replacement for persons with hypothyroidism. Risks 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.Other risks of having blood drawn are slight, but may include:Excessive bleeding Fainting or feeling lightheaded Multiple punctures to locate veins Hematoma (blood buildup under the skin) Infection (a slight risk any time the skin is broken)Open ReferencesReferencesGuber HA, Oprea M, Russell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.Kruse JA. Thyroid disorders. In: Parrillo JE, Dellinger RP, eds. Critical Care Medicine: Principles of Diagnosis and Management in the Adult. 5th ed. Philadelphia, PA: Elsevier; 2019:chap 57.Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 11.AllVideoImagesTogBlood test - illustration Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.Blood testillustrationBlood test - illustration Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.Blood testillustration Tests for TBG blood test TBG blood testT3RU testRelated Information Hypothyroidism(Condition)Liver disease(Condition)Porphyria(Condition)Hyperthyroidism(Condition)Acromegaly(Condition)Acute(Special Topic)Nephrotic syndrome(Condition)Hypothyroidism - InDepth(In-Depth) Review Date: 1/9/2022 Reviewed By: Robert Hurd, MD, Professor of Endocrinology and Health Care Ethics, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. 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TBG blood testSerum thyroxine binding globulin; TBG level; Serum TBG level; Hypothyroidism - TBG; Hyperthyroidism - TBG; Underactive thyroid - TBG; Overactive thyroid - TBG thyroid hormone binding globulinThe TBG blood test measures the level of a protein that moves thyroid hormone throughout your body. This protein is called thyroxine-binding globulin (TBG). How the Test is Performed A blood sample is taken and then sent to a laboratory for testing.Blood sampleVenipuncture is the collection of blood from a vein. It is most often done for laboratory testing.ImageRead Article Now Book Mark Article How to Prepare for the Test Certain drugs and medicines can affect test results. Your health care provider may tell you to stop taking a certain medicine for a short time before the test. Never stop taking any medicine without first talking to your provider.These medicines and drugs can increase TBG level:Estrogens, found in birth control pills and estrogen replacement therapy Heroin Methadone and opioids Phenothiazines (certain antipsychotic drugs)The following medicines can decrease TBG levels: Depakote or depakene (also called valproic acid) Dilantin (also called phenytoin) and carbamazepine High doses of salicylates, including aspirin Male hormones, including androgens and testosterone Prednisone or other glucocorticoids (steroids) How the Test will Feel When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away. Why the Test is Performed This test may be done to diagnose problems with your thyroid. Normal Results Normal range is 13 to 39 micrograms per deciliter (mcg/dL), or 150 to 360 nanomoles per liter (nmol/L).Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results. What Abnormal Results Mean An increased TBG level may be due to:Acute intermittent porphyria (a rare metabolic disorder) Acute intermittent porphyriaPorphyrias are a group of rare inherited disorders. An important part of hemoglobin, called heme, is not made properly. Hemoglobin is a protein in ...ImageRead Article Now Book Mark Article Hypothyroidism (underactive thyroid) Liver disease, such as hepatitis Liver diseaseThe term "liver disease" applies to many conditions that stop the liver from working or prevent it from functioning well. Abdominal pain or swelling...ImageRead Article Now Book Mark Article Pregnancy (TBG levels normally increased during pregnancy) Note: TBG levels are normally high in newborns.Decreased TBG levels may be due to:Acute illness AcuteAcute means sudden. Acute symptoms appear, change, or worsen rapidly. It is the opposite of chronic.ImageRead Article Now Book Mark Article Acromegaly (disorder caused by too much growth hormone) AcromegalyAcromegaly is a condition in which there is too much growth hormone (GH) in your body.ImageRead Article Now Book Mark Article Hyperthyroidism (overactive thyroid) HyperthyroidismHyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive thyroid.ImageRead Article Now Book Mark Article Malnutrition Nephrotic syndrome (symptoms that show kidney damage is present) Nephrotic syndromeNephrotic syndrome is a group of symptoms and abnormal test results that include protein in the urine, low blood protein levels in the blood, high ch...ImageRead Article Now Book Mark Article Stress from surgery High or low TBG levels affect the relationship between total T4 and free T4 blood tests. A change in TBG blood levels can alter the appropriate dose of levothyroxine replacement for persons with hypothyroidism. Risks 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.Other risks of having blood drawn are slight, but may include:Excessive bleeding Fainting or feeling lightheaded Multiple punctures to locate veins Hematoma (blood buildup under the skin) Infection (a slight risk any time the skin is broken)Open ReferencesReferencesGuber HA, Oprea M, Russell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.Kruse JA. Thyroid disorders. In: Parrillo JE, Dellinger RP, eds. Critical Care Medicine: Principles of Diagnosis and Management in the Adult. 5th ed. Philadelphia, PA: Elsevier; 2019:chap 57.Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 11.