Thyroid
TSH Levels by Age: The Chart Your Lab Report Does Not Print
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20267 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
QUICK ANSWER
UK labs print one TSH range for every adult age, usually around 0.4 to 4.0 mU/L. Research disagrees. TSH climbs with age, and the upper figure runs near 4.0 mU/L in your fifties and near 7.5 mU/L past 80. So a mildly raised TSH at 78 means something different from the same number at 38.
Not sure which markers you need? Build your test →You have a TSH of 5.2 mU/L on a page. The range beside it says 0.4 to 4.0, so your number is flagged. You are 71. The obvious question is whether 5.2 is actually high for someone your age, or whether the range was drawn for someone thirty years younger.
It is a fair question. It also has a real answer, and the answer is not the one printed on your report.
1. Is there a TSH range by age in the UK?
Not on your report. UK labs use one adult range, and most sit close to 0.4 to 4.0 mU/L. TSH is thyroid stimulating hormone. It is the signal your pituitary gland sends to tell the thyroid to work harder, so a high TSH means your body is pushing.
Free T4 behaves quite differently across the decades, which free T4 levels by age sets out.
For what a reading above that range means in practice, read high TSH levels.
That single range is applied to an 18-year-old and an 88-year-old alike. The research behind age-specific ranges is solid, but UK labs have not adopted them. Our guide to reference ranges explains how these lines get drawn in the first place.
So the honest position is this. Your lab compares you to every adult. The literature says your age group sits a little higher than the one below it.
2. What do the age figures actually show?
The SORTED 1 trial in the European Thyroid Journal sets out the pattern plainly. It reports that “the 97.5th centile being 4.03 mU/L in the 50–59-year age group and 7.49 mU/L in the 80+ age group”. That is the top of the normal spread nearly doubling across thirty years.
A separate 2022 analysis worked out ranges for older adults directly. Its figures are below.
| Age group | Research range | Against the 4.0 line |
|---|---|---|
| 50 to 59 | up to 4.03 mU/L | About the same |
| 65 to 70 | 0.65 to 5.51 mU/L | Top sits 1.5 higher |
| 71 to 80 | 0.85 to 5.89 mU/L | Top sits 1.9 higher |
| Over 80 | 0.78 to 6.70 mU/L | Top sits 2.7 higher |
The 2022 study put a number on what that changes. Using its age-specific ranges, the share of older people classed as having an underactive-leaning thyroid fell from 10.28% to 3.74%. Two thirds of those flags came from the range, not from the person.
3. Find your own number
Most people arrive holding one value. Here it is written out line by line, against both the lab range and the age research. The right-hand column is what the figure describes, never a diagnosis.
| Your TSH | Lab range | What it describes |
|---|---|---|
| 0.2 mU/L | Below | Low at any age. Read with free T4. |
| 0.4 mU/L | On the line | The bottom figure itself. |
| 1.2 mU/L | Inside | Where most healthy adults sit. |
| 2.5 mU/L | Inside | Comfortably normal. Some clinics call it high-normal. |
| 3.6 mU/L | Inside | Still inside the range at every age. |
| 4.0 mU/L | On the line | Flagged at 35. Mid-range past 70. |
| 4.8 mU/L | Above | Mildly raised. Inside the research range past 65. |
| 5.2 mU/L | Above | Mildly raised. Inside the research range past 65. |
| 6.5 mU/L | Above | Raised. Inside the research range past 80 only. |
| 8.0 mU/L | Above | Raised at every age. Below the NICE treatment figure. |
| 12 mU/L | Above | Above the NICE figure of 10. See your GP. |
One caution on the whole column. A band is not a verdict, and TSH on its own is half the picture. The hormone it controls is free T4, and our free T4 guide covers why the pair get read together. To read an FT4 figure itself, see normal free T4 levels.
A TSH inside its range does not always settle the question. Our guide to a low free T4 with a normal TSH covers the result where the signal looks fine and the hormone does not.
4. Why does TSH drift up with age?
Two things are happening at once, and only one of them is a problem.
The first is thyroid autoimmunity. It becomes more common with age, and it pushes TSH up because the thyroid needs more prompting. That is a genuine change worth knowing about. Our guide to thyroid antibodies covers what that testing adds.
The second is simple ageing of the feedback loop. The pituitary appears to reset slightly higher over the decades, in people with no thyroid disease at all. Studies that exclude everyone with antibodies still find the curve shifting right.
That second group is the one a flat range catches unfairly. They are not ill. The line simply stopped fitting them.
5. What does NICE do with a mildly raised TSH?
This is the reassuring part. UK practice already treats a slightly raised TSH with caution, whatever your age. NICE guideline NG145 says to “consider levothyroxine for adults with subclinical hypothyroidism who have a TSH of 10 mlU/litre or higher on 2 separate occasions 3 months apart”.
Read that carefully. The action figure is 10, not 4. It needs two results, not one. And they must be three months apart.
Below 10, NICE suggests a six-month trial of levothyroxine only for adults under 65 who both sit above the range and have symptoms. Age is written into the guidance itself. Our guide to subclinical hypothyroidism covers that in-between territory in full.
One knock-on worth knowing. An underactive thyroid tends to raise LDL cholesterol, so a raised TSH sometimes arrives alongside a raised cholesterol result. If yours did, our cholesterol blood test guide explains how the two get read together.
6. What else moves TSH besides age?
Quite a lot, and most of it beats age for size.
- Time of day. TSH peaks overnight and is lowest mid-afternoon. A morning sample reads higher.
- Recent illness. TSH falls during illness and can rebound above range in recovery.
- Biotin supplements. High-dose biotin interferes with many thyroid assays. Our guide to supplements that affect blood tests lists the rest.
- Levothyroxine timing. If you take it, the dose and the gap before your sample both matter.
This is why one reading settles very little. NICE asks for two results three months apart for a reason.
7. What to do with a mildly raised TSH
If your figure sits between the top of the lab range and 10, nothing needs to happen today. Four things make the second reading worth more than the first.
- Match the conditions. Same time of morning, same fasted or fed state, both times.
- Wait properly. NICE asks for three months between readings. Testing again in a fortnight rarely helps.
- Leave biotin off. Stop high-dose biotin for a few days first, and tell whoever reads the result.
- Get free T4 measured too. A raised TSH with a normal free T4 is the common picture, and the calmer one.
Bring your age into the conversation with your GP. A TSH of 5.4 at 76 and the same figure at 31 are not the same finding, and the published centiles are the reason why.
8. Which blood test measures your TSH?
Helvy’s Thyroid & Vital Organs panel (£159) reports TSH alongside free T4 and free T3, plus kidney, liver and cholesterol markers. Reading all three thyroid numbers together is what stops a single TSH doing the work on its own.
For a broader first look, the General Energy & Wellness panel (£149) reports TSH and free T4 with cortisol, vitamin D, B12, magnesium and the kidney, liver and cholesterol set. Both are home finger-prick tests, processed by UKAS-accredited UK labs.
Neither panel measures thyroid antibodies, so an autoimmune cause is a separate step to take with your GP. Not sure which fits? The build-my-test tool walks you through it, and the thyroid hub covers the wider picture.
READY TO TEST?
See where your thyroid actually sits
Helvy’s home blood tests report TSH with free T4 and free T3, each explained in words you already use, so one borderline figure never leaves you guessing. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What is a normal TSH level by age in the UK?
UK labs use one adult range at every age, usually around 0.4 to 4.0 mU/L. Research puts the upper figure near 4.0 mU/L at 50 to 59 and near 7.5 mU/L past 80. Your report will use the flat range.
Is a TSH of 5 normal for a 70-year-old?
Your lab will flag it, because 5 sits above 4.0. Published ranges for 65 to 70 run up to 5.51 mU/L, so it falls inside the age figures. NICE only considers treatment from 10 upward. Take the result to your GP rather than acting on it alone.
Do UK labs use age-specific TSH ranges?
No. The research supports them but UK laboratories have not adopted them, so your report compares you against every adult. That is why an older person with a mildly raised figure is worth a second reading before anything changes.
At what TSH does NICE suggest treatment?
NICE guideline NG145 says to consider levothyroxine for adults with subclinical hypothyroidism who have a TSH of 10 mIU/litre or higher on two separate occasions three months apart. Below 10, a six-month trial is considered only for adults under 65 with symptoms.
Does TSH change through the day?
Yes. It peaks overnight and is at its lowest mid-afternoon, so a morning sample reads higher than an afternoon one. Note the time you took your sample, because it changes how a borderline figure should be read.
Should I test free T4 as well as TSH?
It helps. TSH is the signal and free T4 is the hormone that signal controls, so the pair together say far more than TSH alone. A raised TSH with a normal free T4 is a different picture from a raised TSH with a low free T4.
Related panels
Keep reading