What the TSH and free T4 blood tests measure, and why two NHS laboratories print different adult and pregnancy ranges for the same test. What can move a result, whether it needs fasting, where thyroid appears in Egypt's public programmes, and what to ask your doctor.
TSH is thyroid-stimulating hormone, made by the pituitary gland, and a TSH blood test measures it to show how well the thyroid is working (MedlinePlus, updated 30 October 2024). No single range counts as normal everywhere: the range printed on your report, and your doctor, govern.
This page sets out what the TSH and free T4 tests measure, what can move a result, and what to ask. It does not read your result, tell you it is normal, or diagnose anything.
In short:
- TSH is made by the pituitary gland and tells the thyroid how much T4 and T3 to make; free T4 is the T4 not bound to proteins in the blood (NIDDK, last reviewed May 2017).
- Ranges differ by laboratory: two NHS laboratory pages (read 31 October 2026) print adult TSH ranges of 0.27 to 4.2 mIU/L and 0.38 to 5.33 mU/L (table below). MedlinePlus, the NIDDK and the American Thyroid Association’s (ATA) test page print no range at all.
- Pregnancy, age over 80, serious illness elsewhere in the body, some medicines and biotin can change a result.
- MedlinePlus lists no fast for the TSH test itself (updated 30 October 2024).
Last checked: 31 October 2026, on the pages listed under Sources. Guidelines and pages change, so confirm with your doctor.
What is the normal range of TSH?
The pages we read give no single published normal range. MedlinePlus, the NIDDK (the US National Institute of Diabetes and Digestive and Kidney Diseases) and the ATA test page print no TSH or free T4 numbers. The table shows two NHS hospital laboratories in England, only to show that laboratories differ.
| Source | Adult TSH | Adult free T4 | Where this comes from |
|---|---|---|---|
| NHS laboratory A | 0.27 to 4.2 mIU/L | 12.0 to 22.0 pmol/L | Its test page, “last updated” 1 July 2026 |
| NHS laboratory B | 0.38 to 5.33 mU/L | 8.0 to 18.0 pmol/L | Its test page, no date shown, read 31 October 2026 |
Examples, not a standard: each is that laboratory’s own range, not an Egyptian one, and this page cannot say which range your laboratory uses. The range printed on your report, and your doctor, govern.
The same test, two ranges: a number can sit inside one laboratory’s range and outside the other’s. Check the unit beside your number too: these two pages print mIU/L and mU/L.
What do the TSH and free T4 tests measure?
| Test | What it measures | What the source says | Source |
|---|---|---|---|
| TSH | Thyroid-stimulating hormone, made by the pituitary gland | Usually checked first; it tells the thyroid how much T4 and T3 to make. | NIDDK (May 2017); MedlinePlus (30 October 2024) |
| Free T4 | The T4 hormone that is not bound to proteins and can enter body tissues | Many health professionals prefer it because changes in binding proteins do not affect it. The ATA says it reflects how the gland is working more accurately when checked with a TSH. | NIDDK (May 2017); ATA test page (no review date shown, read 31 October 2026) |
The NIDDK (last reviewed May 2017) says a high TSH most often points to an underactive thyroid and a low TSH usually to an overactive one, and that a result that is not normal needs at least one other test to help find the cause. A TSH test cannot show what is causing a thyroid problem (MedlinePlus, updated 30 October 2024). What your result means is for your doctor to say.
What can move a TSH result?
The sources name several things that can change a thyroid blood result. Whether any applies to you is for your doctor. None of them is a reason to start or stop a medicine or supplement on your own: ask your doctor or the laboratory first.
| Factor | What the source says | Source |
|---|---|---|
| Pregnancy | TSH is often a little low in the first three months. Pregnancy also changes the proteins that carry thyroid hormone, which can change total T4 and T3 readings. | MedlinePlus (30 October 2024); ATA test page (read 31 October 2026) |
| Age | TSH may be higher in people over 80 with no thyroid problem. | MedlinePlus (30 October 2024) |
| Serious illness elsewhere in the body | Some serious illnesses not related to the thyroid may lower TSH for a short time; the NIDDK says severe illness can also change T4 results. | MedlinePlus (30 October 2024); NIDDK (May 2017) |
| Medicines | MedlinePlus says you may need to stop certain medicines before the test, but not to stop any unless your provider tells you to. The NIDDK names oral contraceptives and corticosteroids as able to change T4 results. | MedlinePlus (30 October 2024); NIDDK (May 2017) |
| Biotin | The ATA says biotin can make several thyroid tests look abnormal and should not be taken for two days before the blood is drawn; one NHS laboratory page asks for the sample at least eight hours after the last high-dose biotin. The two differ, so tell your doctor or the laboratory about any biotin you take and ask what to do before your test. | ATA test page (read 31 October 2026); NHS laboratory A page (1 July 2026) |
Does the TSH range change in pregnancy?
Yes, on these two pages: each prints a separate TSH range for each trimester, and they differ from the adult range and from each other.
| Source | Adult | 1st trimester | 2nd trimester | 3rd trimester |
|---|---|---|---|---|
| NHS laboratory A (page updated 1 July 2026) | 0.27 to 4.2 | 0.3 to 4.6 | 0.4 to 4.1 | 0.2 to 3.2 |
| NHS laboratory B (no date shown, read 31 October 2026) | 0.38 to 5.33 | 0.05 to 3.70 | 0.31 to 4.35 | 0.41 to 5.18 |
TSH in mIU/L (laboratory A) and mU/L (laboratory B), as each page prints it. Examples, not a standard: the range printed on your report, and your doctor, govern.
An editorial on the ATA’s 2026 and the Royal College of Obstetricians and Gynaecologists’ 2025 pregnancy guidelines says the use of laboratory-specific thresholds is advised (Case Reports in Women’s Health, 20 June 2026). The ATA’s own guideline (Thyroid, May 2026) includes recommendations on thyroid function testing. MedlinePlus (updated 30 October 2024) says anyone with a history of thyroid disease should talk with their provider if they are pregnant or thinking of becoming pregnant. If you are pregnant, ask which ranges your laboratory applies.
Does a thyroid test need fasting?
MedlinePlus (updated 30 October 2024) lists no fast for the TSH test itself and says you may need to fast for several hours if other blood tests are ordered with it. Which blood tests need fasting sets the common tests side by side. For other thyroid tests, and for what your laboratory asks, check with the laboratory.
What should I ask my doctor about my thyroid test?
- Which unit and range does this laboratory print for TSH and for free T4?
- Does this result need to be repeated, and when?
- Could a medicine, a hormone pill, biotin or pregnancy change how this reads?
- Do I need free T4, T3 or antibody tests with it?
- If I take thyroid treatment: when is my next test due?
- If I change laboratory, can the results be compared?
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In Egypt: where do thyroid tests appear in public programmes?
We searched the Ministry of Health and Population and State Information Service (SIS) sites on 31 October 2026 for a page printing TSH ranges and found none, which does not prove none exists. Ask the unit or laboratory you use which range it applies.
Thyroid does appear in two programmes the SIS describes. The presidential newborn screening initiative, launched on 13 July 2021, aims to check babies from the first day with a blood sample from the heel; its SIS page (updated 25 April 2026) lists congenital hypothyroidism among the 19 diseases screened and says the treatment is given free to an affected child. A Ministry of Health and Population statement on the same page (19 April 2026) says the initiative was then in its first phase, which covers premature babies in the incubator units of ministry hospitals, with a second phase to cover all newborns. The page does not say which test is used, and this page cannot say whether it reached your baby: ask the hospital or unit where the baby was born.
On 10 March 2026 the SIS reported that the Egyptian Healthcare Authority had launched a hypothyroidism early-detection initiative in Port Said for women over 35, with a free TSH test for women whose questionnaire answers show possible indicators. It is a Port Said initiative: ask your local unit whether anything similar runs where you live.
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Frequently asked questions
What is the normal range of TSH?
No single range applies everywhere. Two NHS laboratories print adult ranges of 0.27 to 4.2 mIU/L (page updated 1 July 2026) and 0.38 to 5.33 mU/L (no date shown, read 31 October 2026). The range printed on your report, and your doctor, govern.
What is the difference between TSH and free T4?
TSH tells the thyroid how much T4 and T3 to make; free T4 is the T4 not bound to proteins (NIDDK, last reviewed May 2017).
Does the TSH test need fasting?
MedlinePlus (updated 30 October 2024) lists no fast for the TSH test itself; you may need one if other blood tests are ordered with it.
Does the TSH range change in pregnancy?
MedlinePlus (updated 30 October 2024) says TSH is often a little low in the first three months, and two NHS laboratories print trimester ranges that differ from each other (table above). Ask which ranges your laboratory applies.
Medigize is a non-diagnostic navigation tool. This is general information, not medical advice. In an emergency, call an ambulance or go to the nearest emergency department.
Sources
- MedlinePlus (US National Library of Medicine): TSH (Thyroid-Stimulating Hormone) Test, updated 30 October 2024, read 31 October 2026
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): Thyroid Tests, last reviewed May 2017, read 31 October 2026
- American Thyroid Association (ATA): Thyroid Function Tests, no review date shown, read 31 October 2026
- NHS hospital laboratory A (England): Thyroid Function Tests (TSH, FT4, FT3), page last updated 1 July 2026, read 31 October 2026
- NHS hospital laboratory B (England): Thyroid Function Tests, no date shown, read 31 October 2026
- Korevaar TIM, Leung AM, Alexander EK, et al.: American Thyroid Association 2026 Guidelines for Thyroid Disease in Preconception, Pregnancy, and Postpartum, Thyroid 2026;36(5):481–544 (doi 10.1177/10507256261445624), published online 31 May 2026, read 31 October 2026
- Athanasiadou KI, Peppa M, Kalantaridou SN, Paschou SA: Navigating the RCOG 2025 and ATA 2026 guideline updates on the management of thyroid disorders during pregnancy, Case Reports in Women’s Health 2026;51:e00827 (doi 10.1016/j.crwh.2026.e00827), an editorial, 20 June 2026, read 31 October 2026
- Egypt’s State Information Service (SIS): early detection of genetic diseases in newborns (presidential initiative), page updated 25 April 2026, read 31 October 2026
- Egypt’s State Information Service (SIS): the Egyptian Healthcare Authority launches an early-detection initiative for hypothyroidism in Port Said, published 10 March 2026, read 31 October 2026
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