Thyroid Health: Understanding Your Thyroid Through Blood Testing

Your thyroid is a small, butterfly-shaped gland at the base of your neck that produces hormones controlling metabolism, energy production, body temperature, and heart rate. When your thyroid is not functioning properly, it can affect virtually every system in your body.

Thyroid disorders are remarkably common — an estimated 5 to 10 percent of the population has some form of thyroid dysfunction, and many people remain undiagnosed for years because the symptoms overlap with other conditions. Many people who come to us have already been told that their results are normal, yet they still feel cold, tired and not like themselves.

A simple blood draw can measure the hormones your thyroid produces and the signals your brain sends to regulate it. At Wellth, our thyroid panels are analysed by accredited Swedish laboratories with ISO 15189 certification.

Key Biomarkers for Thyroid Health

TSH

The cornerstone of thyroid testing is TSH (Thyroid-Stimulating Hormone), produced by the pituitary gland to signal your thyroid to produce hormones. Elevated TSH typically indicates an underactive thyroid (hypothyroidism), while low TSH may suggest an overactive thyroid (hyperthyroidism). However, TSH alone does not tell the full story.

Free T4

Free T4 (thyroxine) measures the unbound, active form of the primary hormone your thyroid produces. Low Free T4 alongside high TSH confirms hypothyroidism.

Free T3

Free T3 (triiodothyronine) is the most metabolically active thyroid hormone — your body converts T4 into T3 in tissues. Some individuals have poor T4-to-T3 conversion, which TSH and Free T4 testing alone would miss.

Antibodies

Thyroid antibodies (TPO-Ab and TG-Ab) help identify autoimmune thyroid conditions such as Hashimoto's thyroiditis or Graves' disease, which are the most common causes of thyroid dysfunction in Sweden. Together, these markers provide a comprehensive picture of your thyroid health. It is also possible to have raised thyroid antibodies while TSH, Free T4 and Free T3 are all normal.

The antibodies show that the immune system has begun to react to the thyroid. They often appear years before hormone levels change, so they are one of the earliest signs a blood test can pick up.

Thyroid Complete Panel →TSH Test →

Signs You Should Get Your Thyroid Tested

  • Unexplained weight gain or difficulty losing weight
  • Persistent fatigue despite adequate sleep
  • Feeling unusually cold or heat-intolerant
  • Dry skin, brittle nails, or thinning hair
  • Brain fog, poor concentration, or memory problems
  • Mood changes including depression or anxiety
  • Irregular menstrual cycles or fertility difficulties
  • A family history of thyroid disease or autoimmune conditions
  • Swelling or discomfort in the neck area
  • Unexplained changes in heart rate

What Your Results Might Show

Raised TSH

If your TSH is elevated above the reference range (typically above 4.0–4.5 mIU/L) and your Free T4 is low, this pattern is consistent with hypothyroidism — your thyroid is underproducing hormones. You may experience fatigue, weight gain, and cold intolerance.

Low TSH

If your TSH is suppressed (below approximately 0.4 mIU/L) and your Free T4 or Free T3 is elevated, this pattern suggests hyperthyroidism, which can cause weight loss, anxiety, tremors, and rapid heartbeat.

Subclinical changes

Subclinical thyroid dysfunction occurs when TSH is outside the normal range but Free T4 and Free T3 remain normal — this is an early stage that warrants monitoring.

Antibodies

Positive thyroid antibodies (TPO-Ab or TG-Ab) indicate an autoimmune process, even if your hormone levels are currently normal.

Normal results but symptoms

Results within the reference range are described as euthyroid, meaning your thyroid is currently producing enough hormone. Many people with euthyroid results still have symptoms, so in our clinic we start with how you feel and read your results with that in mind. Reference ranges are broad.

Your thyroid also needs iron, selenium and iodine, and it slows down with long-term stress and very low-calorie eating.

Your report

Your Wellth health report will explain exactly where your values fall, whether they are optimal or simply within the standard reference range, and what steps to consider next.

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Frequently Asked Questions

How often should I test my thyroid?
If you have no known thyroid issues, testing once a year is generally sufficient. If you are managing a thyroid condition or taking thyroid medication, your report may recommend testing every 3 to 6 months to monitor your levels and adjust treatment.
Do I need to fast before a thyroid blood test?
Fasting is not strictly required for thyroid tests, but we recommend testing in the morning before eating for the most consistent TSH readings, as TSH levels naturally fluctuate throughout the day and are highest in the early morning.
Can stress affect my thyroid results?
Yes. Chronic stress can affect the hypothalamic-pituitary-thyroid axis, potentially altering TSH and thyroid hormone levels. Acute illness can also temporarily affect thyroid function tests. If you have been under significant stress or are unwell, mention this to your practitioner when reviewing your results.
What is the difference between subclinical and overt hypothyroidism?
Subclinical hypothyroidism means your TSH is elevated but your Free T4 and Free T3 are still within the normal range — you may or may not have symptoms. Overt hypothyroidism means both TSH is high and Free T4 is low, and symptoms are typically more pronounced. Subclinical hypothyroidism can progress to overt hypothyroidism over time, which is why monitoring is important.
Raised TPO antibodies but normal TSH: what does it mean?
Raised TPO or TG antibodies mean your immune system is reacting to your thyroid, but your thyroid is still producing enough hormone. Many people stay in this state for years, while some gradually develop an underactive thyroid, so regular follow-up is worthwhile. Antibodies are also important to know about if you are planning a pregnancy or have another autoimmune condition such as coeliac disease.
Are Hashimoto's and hypothyroidism the same thing?
No, although they are closely linked. Hashimoto's thyroiditis is an autoimmune condition in which the immune system gradually damages the thyroid, and it is the most common cause of hypothyroidism in Sweden. Hypothyroidism simply means the thyroid is producing too little hormone. You can have Hashimoto's with normal hormone levels for many years, and hypothyroidism can have other causes, such as thyroid surgery or certain medicines.
Low T3 but normal TSH: what does it mean?
A low Free T3 with normal TSH and Free T4 is often not a sign of thyroid disease. It usually means your body is converting less T4 into active T3, which happens during illness, long-term stress, very low-calorie eating and hard training. It is worth finding out what is behind it.
Which tests should you take for the thyroid?
TSH and free T4 are the basis. Free T3 shows how much active hormone you have, and antibodies (TPO and TG) show whether the immune system is reacting against the thyroid. Ferritin is also worth including.
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Reviewed by

Wellth Team

Wellth

Our content is written and reviewed by Wellth, and fact-checked against peer-reviewed research and current Swedish clinical guidelines.

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Important to know

Wellth does not diagnose or treat disease. We work with diet, lifestyle and preventive health, alongside the care you already have.

Our reports and sessions do not replace medical advice, and a test result should not be read as a diagnosis. We use both standard healthcare reference ranges and optimal ranges. A value can therefore be normal by healthcare standards and still fall outside the range associated with good health. That does not mean disease, but it can be a chance to act early.

Supplements are only recommended by a nutritional therapist as part of a consultation, never automatically from a test result.

If anything in your results needs to be looked at by a doctor, we will tell you clearly. Contact your healthcare provider if you are worried about your health. Call 1177 for advice, or 112 in an emergency.