What changes for women and men

Normal blood test results for females differ from those for males on several lines, and hemoglobin is the clearest case: a 2024 analysis of healthy people from eight countries put the lower limit at about 12.0 g/dL for non-pregnant women and 13.5 g/dL for men. A hemoglobin of 12.8 g/dL 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 equations that turn creatinine into an estimated filtration rate (eGFR) use age and sex as stand-ins for muscle. 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 report prints 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.

  1. HemoglobinA lower floor in women than in men from adolescence onwards; boys and girls are similar before that.
  2. FerritinRuns lower in women before menopause, and the point at which it matters for red cells differs by sex and age.
  3. CreatinineHigher on average in men because it comes from muscle; read it with the eGFR, which already adjusts for sex.
  4. Kidney filtrationDeclines with healthy aging, so the same eGFR carries a different meaning at 30 and at 80.

Menstruation, menopause and iron

Ferritin, the usual measure of iron stores, shows how much life stage matters. In a 2026 study of 7,990 healthy US adults, average ferritin was about 102 ng/mL in premenopausal women against 258 ng/mL in men under 53, and serum iron was also lowest in premenopausal women.

The same study found that a substantial share of these healthy people fell outside commonly used ranges, especially for serum iron and transferrin saturation. A separate analysis of more than 48,000 adults at a Boston hospital found that the ferritin level from which more iron went with better red cell values differed by group: about 15 ng/mL in younger women, 25 in older women and 35 in men.

That is why one printed ferritin range, or even one range per sex, can fit some people poorly. If your ferritin sits near the floor, ask your doctor how it should be read for your age and, for women, before or after menopause.

What age shifts, and how slowly

Children are not small adults for laboratory purposes. Their values change through infancy and adolescence, so pediatric ranges are set by age and sex, and a 2026 US study used the results of 51,863 children to check that such ranges fit an American outpatient population. Hemoglobin shows the pattern: its lower limit rises from about 10.4 g/dL in toddlers to 11.4 g/dL at 5 to 11 years, and boys and girls only separate in adolescence. A child’s report should never be read against an adult table.

In adults the shifts are slower and fewer. Kidney filtration declines with healthy aging, 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. If your eGFR is flagged in later life, ask whether a urine albumin test is part of reading it.

Pregnancy has its own ranges

Pregnancy shifts several lines trimester by trimester: a 2024 analysis put the hemoglobin floor at about 11.0 g/dL in the first trimester, and a 2021 review warns that most laboratories still print non-pregnant ranges on pregnancy results. The tests themselves, the schedule and the values pregnancy moves are covered in the guide to prenatal blood tests; read any flag on a pregnancy report with your obstetrician or midwife. The glucose test of pregnancy has its own guide to gestational diabetes test results.

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 report, because it depends on the analyzer, 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 or men 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. The trend is the part of your file that nobody else has.