T3 (Triiodothyronine) Test

T3 test is done to assess thyroid function. It is recommended to individuals who show apparent symptoms of hypo or hyperthyroidism.

Some symptoms of hyperthyroidism are:

• Anxiety
• Weight loss
• Increased heart rate
• Weakness
• Diarrhoea
• Difficulty in sleeping
• Tremors
• Puffiness around the eyes
• Sensitivity to light
• Irregularity in the menstrual cycle in females

Symptoms of hypothyroidism include:

• Sudden weight gain
• Constipation
• Dryness in the skin
• Fatigue
• Loss of hair
• Intolerance to cold
• Shortness of breath
• Slow heart rate
• Puffiness in the skin
• Irregularity in the menstrual cycle in females

(Read more: Thyroid function test)

No special preparation is usually needed for this test. It can be done at any time of the day, and no fasting is required. However, some medicines can alter the results of a T3 test; hence, you must inform your doctor about the medications you are taking. He/she may advise you to stop taking certain medicines, such as birth control pills, clofibrate, oestrogen, methadone, certain herbal remedies, amiodarone, anabolic steroids, androgens, anti-thyroid drugs, lithium, phenytoin and propranolol. Also, the test should be avoided in case you are suffering from an acute illness.

To perform this test, a sample of blood will be drawn from a vein of your arm using a needle. The needle injection site will first be cleaned with alcohol before collecting the required amount of blood.

After the test, the injection site will be pressed firmly, and a cotton or gauze pad will be placed over that area to stop bleeding. The collected blood sample will be sent to a lab. for examination.

The whole process is painless and noninvasive, but few people experience slight redness in the area of needle insertion. The redness can be minimised by placing an ice pack over the affected area.

The test results can vary depending upon the method used and the age, gender, and health history of the person. A healthcare provider will provide the correct interpretation of your results.

Normal results: The normal range of free T3 hormone is 4-7.4 picomoles per litre (pmol/L)

Abnormal results: If the test result shows a higher than normal T3 level, it can be due to any of the following conditions:

• Overactive thyroid gland 
• T3 thyrotoxicosis (elevated serum T3 and normal T4 concentration)
• Toxic nodular goitre (autonomously functioning thyroid nodules in a thyroid gland)
• Liver disease
• Intake of thyroid medicines or certain supplements 
• First trimester of pregnancy
• Intake of birth control pills or oestrogen

If the test result shows a lower than normal T3 level, it can be indicative of the following conditions:

• Severe illnesses (short term or long term)
• Thyroiditis (swelling or inflammation of the thyroid gland)
• Starvation or malnutrition
• Underactive thyroid gland

(Read more: T4 test results)

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.