Free T4 – what do your numbers mean?
Have you had your Free T4 level measured and are unsure what the numbers mean? Here you'll find a clear explanation of the normal range, what a high or low level can indicate, and when it makes sense to get tested.
What is the normal range for Free T4?
What is the normal range for Free T4?
The normal range for Free T4 (fT4) in adults over 20 years typically lies between 12.0 and 21.0 pmol/L. For children and adolescents, values vary with age, for example 13.0-22.0 pmol/L for children between 6 and 11 years. During pregnancy, levels change and are lower in the second and third trimesters, with reference intervals of 10.0-17.0 pmol/L and 8.0-16.0 pmol/L, respectively. These variations are due to hormonal changes and physiological adaptations. Reference intervals can vary between laboratories depending on the methods used. Being close to the limit values can indicate incipient hypo- or hyperthyroidism, which may necessitate further investigations.
What does a low level mean?
A low level of Free T4 can indicate hypothyroidism, where the thyroid gland produces insufficient amounts of thyroid hormone. Symptoms can include fatigue, weight gain, cold intolerance, dry skin, and hair loss. Causes can be autoimmune diseases such as Hashimoto's thyroiditis, iodine deficiency, or side effects of medication. Particularly vulnerable groups include the elderly, pregnant women, and individuals with a family history of thyroid diseases. If a low level is detected, a doctor should be contacted for further assessment and possible treatment, which often involves synthetic thyroxine supplementation.
What does a high level mean?
A high level of Free T4 can be a sign of hyperthyroidism, where the thyroid gland produces too much thyroid hormone. Typical symptoms include weight loss, palpitations, nervousness, sweating, and sleep problems. Common causes are Graves' disease, toxic nodular goiter, or thyroxine overdose. It is important to seek medical attention if these symptoms are experienced, as untreated hyperthyroidism can lead to serious complications such as heart problems and osteoporosis. Treatment may include medication, radioactive iodine, or surgery depending on the cause and severity.
Get your Free T4 level tested
At Celto, you can order a blood test for Free T4 directly online – without a referral from your doctor and without long waiting times. We have over 34 sample collection sites at public hospitals across Denmark, and your samples are analyzed in the same accredited laboratories used by the rest of the healthcare system. You will receive your results directly on sundhed.dk, just like all other blood tests from the public system.
How it works
When you order a blood test from Celto, you choose which markers you want to be tested – no doctor's referral necessary. After your purchase, you will receive an email with a link to our booking system, where you choose time and location. The blood sample itself is taken by authorized healthcare personnel and typically only takes a few minutes.
Where you can get tested
Celto has over 34 sample collection sites at public hospitals and clinics throughout Denmark. You choose the location that suits you best among our partners, and there are typically available appointments within a few days. Find your nearest sample collection site →
How you get your results
Your blood samples are analyzed in the same laboratories used by your GP and the rest of the healthcare system, with the exact same quality and same tests. You will receive your results directly on sundhed.dk within a few working days, and Celto will also send an easy-to-understand overview of your values so you know what the numbers mean.