Which thyroid tests do you need?
Tests worth discussing with your doctor
TSH is the first and most sensitive test when a thyroid function problem is suspected — it shows whether hormone production is too low or too high, and it is usually ordered when someone reports fatigue, weight changes or an irregular heartbeat.
Source: MedlinePlus – TSH (Thyroid-Stimulating Hormone) Test
Free thyroxine (FT4) shows how much active hormone is actually circulating in the blood, and it is usually tested together with TSH when symptoms suggest an underactive (hypothyroidism) or overactive (hyperthyroidism) thyroid.
Free triiodothyronine (FT3) complements the TSH and FT4 results, especially when an overactive thyroid is suspected — unexpected weight loss, nervousness, a racing heartbeat or heat intolerance.
Thyroid peroxidase antibodies (TPOAb) help determine whether the cause of a hormone disorder is autoimmune, which affects how often testing should be repeated afterwards.
Source: MedlinePlus – Thyroid Antibodies
Sources
- MedlinePlus – TSH (Thyroid-Stimulating Hormone) Test — 2026-09-06
- MedlinePlus – Thyroxine (T4) Test — 2026-09-06
- MedlinePlus – Triiodothyronine (T3) Tests — 2026-09-06
- MedlinePlus – Thyroid Antibodies — 2026-09-06
Why these tests matter
Thyroid hormones regulate metabolism, so too little or too much of them can show up as a wide range of symptoms — fatigue, weight changes, mood swings, an irregular heartbeat, hair loss, or changes in the menstrual cycle. The TSH test shows whether the pituitary gland is signalling the thyroid to work harder or slower, and it is the most sensitive first indicator of a functional problem. If TSH is outside the normal range, free thyroxine (FT4) and free triiodothyronine (FT3) are tested next — they show how much hormone is actually circulating in the blood, which helps distinguish whether tissues are already affected or the pituitary is only compensating for a small shift. A test for thyroid peroxidase antibodies (TPOAb) helps determine whether the cause is autoimmune (for example, Hashimoto's disease), since that affects how often follow-up testing is needed. It's important to understand what these tests can and cannot do: they show hormone levels and immune activity at a single point in time, but results alone are not a diagnosis — they are always interpreted together with symptoms, a physical exam and, when needed, imaging. A single result also cannot capture the long-term course of the condition or predict how the gland will behave in the future.
When not to wait
- You notice a fast or irregular heartbeat, strong tremor, or sudden weight loss — don't wait for a routine test, see a doctor as soon as possible.
- You notice a visible or rapidly growing swelling or lump in your neck, or difficulty swallowing.
- Symptoms appear during pregnancy or while planning one — thyroid function is then assessed more urgently.
- Symptoms are severe and interfere with daily life (marked fatigue, difficulty concentrating, pronounced mood changes) — don't wait for them to pass on their own.
When to seek care immediately
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
Frequently asked questions
›What symptoms can point to a thyroid disorder?
Too little or too much thyroid hormone can show up as tiredness, weight changes, hair loss, intolerance to cold or heat, mood swings, a feeling of a racing heart or heart rhythm problems, and changes in the menstrual cycle. Symptoms alone do not confirm a diagnosis: the first test is TSH, and a doctor assesses the results together with your symptoms and an examination.
›Are these tests free?
If your family doctor (Lithuania's primary care physician, similar to a GP) suspects a thyroid disorder based on your symptoms, they can refer you for testing through the National Health Insurance Fund (VLK — the Lithuanian agency that administers mandatory state health insurance) system, in which case the tests are covered. Without a medical indication, tests ordered independently at a laboratory are paid for by the patient.
›Who should I contact about thyroid tests?
It's best to start with your family doctor (GP), who will assess your symptoms and, if needed, order tests or refer you to an endocrinologist for further evaluation.
›Why are several markers tested, not just TSH?
TSH reflects the overall activity of the pituitary–thyroid axis, but FT4, FT3 and the antibody test help pinpoint the nature and likely cause of a disorder more precisely when TSH is outside the normal range.
›Can thyroid tests be done in Kaunas?
Blood tests for thyroid hormones and antibodies are available at many laboratories operating in Kaunas as well, either with a family doctor's referral or ordered independently.
›Does one normal TSH result mean the thyroid is healthy for good?
No — the result only reflects your status at that moment, and thyroid function can change later, so recurring or newly appearing symptoms are a reason to get tested again.
›What does it mean if TPOAb antibodies are elevated but TSH is normal?
This can indicate an autoimmune tendency that isn't yet affecting hormone production. In that case, a doctor usually recommends only closer monitoring of thyroid function going forward.
Related situations
How to prepare
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.