What Is a Normal Thyroxine Level?

Thyroxine is a hormone produced by the thyroid glands. It regulates metabolism by controlling the rate of oxidation in the cells. Thyroxine is also 65 per cent iodine. A lack of or overabundance of thyroxine can cause several health concerns, so thyroxine levels should be regulated for optimum health.

Normal Range

According to, the U.S. National Library of Health Medicine's website, the normal range of thyroxine levels are 4.5mcg to 11.2mcg per decilitre of blood. While this is the accepted standard for normal levels of thyroxine, there may be a small variance on preferred levels, depending on the doctor and laboratory.


Numbers lower than 4.5mcg may indicate hypothyroidism, which is caused by an underactive thyroid. Symptoms indicative of hypothyroidism include a slow pulse, dry cool skin, white patches of skin without pigment, weak nails, brittle hair, slow reflexes, slow speech and enlarged heart. Goitre, which can be a result of an enlarged thyroid, may also be a sign of low levels of thyroxine in the blood. Many patients also complain of severe intolerance to the cold, weight gain, tiredness, weakness, joint and muscle pain or stiffness, constipation, increased menstruation, memory trouble, lack of concentration, ringing in the ears, and insomnia.

Hypothyroid Related Conditions

Low levels of thyroxine cause metabolic changes in the body's systems, which can lead to other conditions. Increased total cholesterol levels are often a problem, as well as increased LDL cholesterol, decreased HDL, and increased triglycerides. The chance of heart attack and stroke increases in people with hypothyroidism. Another problem common for people suffering from hypothyroidism is a reduced sex drive, increased possibility of miscarriage and high blood pressure during pregnancy.


Any number higher than 11.2mcg of thyroxine per decilitre of blood may indicate different serious health conditions, due to an overactive thyroid. Conditions usually associated with an overactive thyroid are Graves disease, Germ cell tumours, chronic thyroiditis, toxic multimodal goitre and trophoblastic disease. Symptoms of a hyperthyroid include a problem called lid lag, which is typified by eyes that appear to be protruding from the lids and the inability of the upper lid to follow the eye downward when looking down. A person suffering from hyperthyroidism may experience excessive sweating over the entire body, a condition that keeps the skin moist and warm at all times.

Hyperthyroid Related Conditions

Plummer's Nails is a condition that results from high levels of thyroxine. This ailment is signified by the rising up of the end portion of the nails. Dirt is easily trapped inside the nail tips, and it may be hard to keep them clean. This condition begins on the fourth finger of each hand and then spreads to the other fingers and toes. However, the most serious medical problems that may develop in hyperthyroid patients are a rapid pulse rate and heart palpitations. Both of these conditions can cause an irregular heart rhythm and even heart failure.

Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Susan Elliott teaches studio art and creative writing to home schooled students. She is a graduate of Northwest Arkansas Community College and the Memphis School of Preaching Student Wives Program. She has written for Christian Woman Magazine and Virtuous Magazine. When she's not writing, she is painting or making costumes.