Normal blood test results for women, and what age and pregnancy change

Which lines differ for women

Normal blood test results for women differ from men’s on a handful of lines, and haemoglobin is the clearest. NHS laboratories print a lower floor for women: 115 g/L at one Gloucestershire trust and 120 g/L in Leeds, against 130 g/L for men at both. A haemoglobin of 125 g/L is therefore within range for a woman and can be flagged low for a man.

Creatinine differs for another reason. It is made by muscle, and because average muscle mass differs, the Leeds laboratory prints 49 to 90 µmol/L for women and 62 to 115 for men. The equation that turns creatinine into an estimated filtration rate (eGFR) takes age and sex into account, and NICE warns it is less reliable at extremes of muscle mass. The difference in the range reflects muscle more than the kidneys themselves.

The practical consequence is that a range is never just a range. It is a range for a group, and your results print the one for the group the laboratory assigned you to. If your sex or date of birth was recorded wrongly, the flags on the page can be wrong too, and that is worth checking.

Periods, menopause and iron

Ferritin, the usual measure of iron stores, is where life stage shows most. British gastroenterology guidance lists menstrual blood loss among the common mechanisms of iron deficiency, alongside poor intake and blood loss from the gut.

Ranges reflect this unevenly. The Gloucestershire laboratory prints 11 to 310 µg/L for women and 24 to 340 for men, while Leeds uses a single adult range of 30 to 337, taking its floor from NICE guidance on iron deficiency. The same guidance treats a ferritin below 15 µg/L as absent iron stores and below 30 as generally low, so a ferritin of 20 can look ‘in range’ on one set of results and low on another.

Ferritin also rises with inflammation, so a normal-looking result during an infection can hide low iron. And life stage changes how a low result is followed up: in men and in women after the menopause, about a third of those with iron deficiency anaemia turn out to have an underlying cause, most often in the gut, which is why it is investigated further. If your ferritin sits near the floor, ask your GP how it should be read for your age and stage of life.

What age shifts, and how slowly

Children are not small adults for laboratory purposes. Their values change through infancy and adolescence, so children’s ranges are set by age: the Leeds laboratory, for example, gives separate haemoglobin ranges from the first days of life to 16, and an international analysis found boys and girls only separate in adolescence. A child’s results should never be read against an adult table.

In adults the shifts are slower and fewer. Kidney filtration declines with healthy ageing, without other signs of kidney damage. A large review found that the eGFR below which the risk of death rises is about 75 in younger adults but 45 in older ones, and its authors argue that the threshold used to define kidney disease should depend on age.

A 2023 review adds that in older people an eGFR between 45 and 59 without protein in the urine does not carry a higher relative risk of kidney failure or death. NICE’s own classification does not count an eGFR of 60 to 89 as kidney disease unless there are other markers of kidney damage, and reads eGFR together with a urine albumin test (ACR). If your eGFR is flagged in later life, ask whether an ACR is part of reading it.

Pregnancy has its own ranges

Pregnancy changes the body’s chemistry trimester by trimester. UK guidance from the British Society for Haematology defines anaemia in pregnancy as a haemoglobin below 110 g/L in the first trimester, below 105 g/L in the second and third, and below 100 g/L after the birth, well under the floors used outside pregnancy.

Thyroid, liver, kidney and blood count markers all shift, and a 2021 review warns that most laboratories still apply non-pregnant adult ranges to pregnant women. That matters most for thyroid tests, whose expected values change with each trimester.

A pregnancy result read against non-pregnant ranges can look alarming, or reassuring, for the wrong reasons. If you are pregnant, ask whether pregnancy-specific ranges were applied, and go through the results with your midwife or GP.

What tables like this cannot tell you

A range published anywhere, including here, is a reading aid. The one that applies to your value is printed beside it on your results, because it depends on the analyser, the reagents and the population that laboratory serves.

Ranges also leave healthy people outside them: about one in twenty on any single test. A 2025 review in the Journal of the American Board of Family Medicine notes that the number of results outside the normal range far exceeds the number that are clinically meaningful. A table answers the question of what is usual for women of your age; it does not answer what is happening to you.

The comparison that beats every table

Your own previous result. A value that has sat just outside its range for three years, unchanged, is a different finding from the same value arriving for the first time, and no band by sex or age can make that distinction for you.

Laboratory scientists have tools for exactly this: they can calculate how big a change between two of your results must be before it exceeds the normal day-to-day variation of a test. Ask whether a change you notice clears that bar. In England, older results may not appear automatically in the NHS App if the test was done before October 2023; your GP surgery can make them available.