Thyroid Blood Test
3 Biomarkers | Venous or Capillary Blood Test | CE-marked | UKAS-accredited | Doctor-reviewed results with personalised interpretation.
A thyroid function check measuring TSH, FT4 and FT3. Designed for people investigating tiredness, weight changes, low mood, cold sensitivity or energy changes, this test gives clear, clinically reviewed insight so you can understand your results and know what to do next.
Results are typically available within 2 working days from when your sample reaches the laboratory (excluding weekends and bank holidays).
Thyroid Function
- Free Thyroxine, FT4
- Free Triiodothyronine, FT3
- Thyroid Stimulating Hormone
How to prepare
- Fasting required 8–12 h before the test (water only) recommended for glucose, cholesterol/triglyceride accuracy
- Sample timing: between 7:00 AM – 10:00 AM
- Stay hydrated; avoid strenuous exercise, heavy meals, and supplements (iron, B12, multivitamins, biotin) for 48 hours prior
- Continue prescribed medications unless otherwise directed
Frequently asked questions
Who is this test for?
It is for adults with symptoms that may indicate a thyroid disorder, such as fatigue, weight change, feeling cold, hair thinning, low mood or palpitations. It provides a core assessment of thyroid function.
Should I stop biotin supplements before testing?
Yes. Stop biotin containing supplements, including many hair, skin and nail products and some B complex formulations, for at least 48 hours. Biotin interferes with the laboratory method used for thyroid testing and can produce results that appear falsely high or low.
I take levothyroxine. When should I test?
Take your sample before your daily dose, ideally in the morning, and keep the timing consistent each time you retest. Taking levothyroxine shortly before the test raises measured T4 and makes results difficult to compare.
Do I need to fast?
Fasting is not required. TSH is slightly higher early in the morning, so if you are monitoring an existing thyroid condition, testing at a consistent time makes changes easier to interpret.
How does this differ from the Advanced Thyroid panel?
This is the core assessment. The Advanced Thyroid Blood Test adds thyroid antibodies and a fuller range of thyroid hormones, which matters if you are investigating an autoimmune cause such as Hashimoto's or Graves' disease.