Do blood test results change with age?
For most tests, no. B12, ALT (liver) and blood count ranges match at 25 and 75. A few drift with age, and some labs split testosterone by age. Your best yardstick isn’t a chart.
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Do blood test ranges change with age?
For most tests, no. Adults share one range from decade to decade, sometimes split for men and women. Children have their own.
So NICE uses the same B12 cut-offs for everyone over 16. A B12 of 400 reads the same at 30 as at 70.
| Test | Adult level | Age bands for adults? |
|---|---|---|
| Haemoglobin (the part of red blood cells that carries oxygen) | 130 to 170 g/L (men), 120 to 150 g/L (women) at one NHS lab | No. Children have their own. |
| ALT (liver) | 41 U/L or less (men), 33 or less (women) at one NHS lab | No |
| Vitamin B12 (total) | Below 180 ng/L: low B12 confirmed. 180 to 350: possible. Above 350: unlikely. | No |
| Total cholesterol | Below 5 mmol/L, the NHS guide for healthy adults | No. Your GP may set your own goal using your age and risk. |
| HbA1c (blood sugar) | 42 to 47 mmol/mol: prediabetes. 48 or more: diabetes. | No |
| eGFR (kidney filter) | 60 or more: no kidney disease unless there are other signs of damage | No. But the number itself falls with age. |
Sources: UHD NHS; Liverpool NHS; NICE NG239; NHS; Diabetes UK; NICE NG203
Haemoglobin by age? Children’s levels run lower: one NHS lab uses 110 to 140 g/L for ages 2 to 6. More in haemoglobin levels by age.
ALT by age? That lab splits by sex, not age. See normal ALT levels.
Labs differ a little, and NICE says to use the lab’s own B12 cut-offs where they vary. So check your number against the range printed on your own report.
Which blood test results change with age?
Five common ones drift as you get older. The range on your report usually stays put while your number moves. TSH can move past the top of it, and a few ranges do change with age.
ESR (a test for swelling, or inflammation, in the body) is one. One NHS lab’s upper limit rises from 10 at 50 or under to 30 over 70 in men, and from 12 to 35 in women.
| Test | Which way | By how much |
|---|---|---|
| eGFR (kidney filter) | Falls | About 1 a year. Typical level about 110 at 35, 80 to 85 at 75 (German study). |
| TSH (a signal to the thyroid, the gland in your neck) | Rises | Top of the usual spread: 3.56 mU/L at 20, 7.49 at 80 (US survey). |
| HbA1c (blood sugar) | Creeps up | About 1 to 1.5 mmol/mol a decade, even without diabetes (US studies). |
| Total cholesterol | Rises to midlife | Raised in 72% of adults aged 45 to 64 (England, 2021). |
| Testosterone (men) | Falls slowly | About 1% a year from around age 30 to 40 (NHS). |
Sources: Gutenberg Health Study; Mammen 2019; Diabetes Care; NHS England survey; NHS; Liverpool NHS
Testosterone in nmol/L by age? Some NHS labs print an age-split range. One uses 8.6 to 29 for men aged 20 to 49, and 6.7 to 25.7 for men 50 and over.
The NHS says the slow fall is unlikely to cause problems in itself.
UK sexual health experts (the BSSM) usually advise treatment below 12 nmol/L on two morning tests, in men with symptoms. Their line has no age bands. They say a lab’s range describes most men, while their line is for men with symptoms.
An eGFR of 60 to 89? NICE calls that a mild drop compared with a young adult. It’s not kidney disease without other signs of damage.
Each has its own guide: eGFR, TSH, blood sugar, cholesterol and testosterone by age.
Is normal for my age good enough?
Not always. An age average tells you what’s common, not what’s healthy.
Source: Health Survey for England 2021
So a typical result at 55 can still sit above the NHS healthy level of below 5. Being average isn’t the same as being fine.
The trap runs the other way too. In one US survey, 1 in 10 older adults with no thyroid disease had a TSH above the usual range.
NICE also allows for age. It suggests trying thyroid treatment for a mildly raised TSH only in adults under 65. It must be above the range but below 10 on 2 tests, 3 months apart, with symptoms.
Got a flagged result? Ask your GP whether it needs a repeat test before anything else.
How do I compare my results as I get older?
Your best yardstick is your own last result. A chart shows other people. Your trend shows you.
Kidney numbers show why. Losing about 1 point of eGFR a year is the usual pace. In adults with kidney disease, NICE advises a specialist check for a lasting fall of 15 or more in a year.
Five ways to make your results easy to compare
- Keep every result with its date and the range printed beside it.
- Use the same lab when you can, because cut-offs can differ between labs.
- Book testosterone tests between 8 and 11am, as the BSSM advises.
- Taking B12 tablets, injections or patches? Say so before a B12 test, because they may raise the result without fully fixing a low level.
- Ill lately, taking some medicines or had a baby? Your cholesterol may read lower or higher, so ask whether to test later.
Sources: NICE NG239; BSSM; NHS
On metformin (a diabetes medicine) or stomach acid tablets? NICE lists both as risk factors for low B12, so ask your GP whether a B12 test makes sense. Never stop or change a prescribed medicine without your prescriber.
Aged 40 to 74 in England? You should be invited to a free NHS Health Check every 5 years. It includes a cholesterol test.
The exception is if you already have certain conditions, such as heart disease, diabetes or kidney disease. Then you should be offered regular check-ups instead.
Vitamin D by age? The NHS advises the same daily amount for every adult: 10 micrograms. Consider it in autumn and winter.
Take it all year if you’re rarely outdoors, for example frail or housebound, live in a care home or cover most of your skin outdoors. With dark skin, consider it all year too. More in vitamin D levels by age.
When to speak to a GP
Book a GP appointment if:
- Your eGFR is below 60 for the first time. NICE advises a repeat test within 2 weeks to confirm it.
- Your HbA1c is 42 or more. If you had no symptoms, a diabetes result needs a second test to confirm it.
- You think you may be low in B12. Signs include extreme tiredness, low energy, pins and needles, a sore red tongue, mouth ulcers and weak muscles. Others are eyesight problems, low mood, anxiety, confusion, or trouble with memory, understanding and judgement. The NHS says see a GP.
- You’re a man with low mood, low sex drive, erection problems, mood swings, less muscle or more belly fat. Low energy, poor sleep and poor memory count too. The NHS says see your GP, who may check your testosterone.
Feel very unwell, or symptoms came on quickly? Get an urgent GP appointment or call 111.
To read every line of a report, see blood test results explained and UK reference ranges.