Type the hemoglobin result from your blood test, pick its unit and who it is for. You see it against the NIH’s line and the WHO’s 2024 line for that group — with the WHO’s own corrections for altitude and smoking — and where the two disagree, both. Your lab’s range, and your doctor, have the last word.
13 g/dL is
Not under either source’s line NIH ODS’s 12 g/dL · the WHO’s 120 g/L
13 g/dL = 130 g/L = 8.1 mmol/L
| Line | In the source’s words | Your 13 |
|---|
This is not medical advice and it does not diagnose anything. It shows where a number sits against published lines; what your result means for you depends on your other blood results, your history and your doctor.
NIH’s Office of Dietary Supplements says “Hemoglobin concentrations lower than 11 g/deciliter (dL) in children under 10 years of age, or lower than 12 g/dL in individuals age 10 years or older, suggest IDA” (iron deficiency anemia). The WHO’s 2024 guideline draws its anaemia line at 120 g/L (12 g/dL) for women, 130 g/L for men, and 105–110 g/L in pregnancy.
How to use it
Find “Hemoglobin” (Hb, Hgb) on your blood count and type the number, then pick the unit printed beside it: US labs report g/dL, most others g/L, and a few mmol/L. Pick who the test is for. If you live above 500 metres or smoke, say so: the WHO corrects for both, because each raises hemoglobin. You see every line that applies, in its source’s words, and where your result sits against each — with MedlinePlus’s common lab range for adults beside them. It does not tell you what to take: that is the conversation with your doctor.
The lines, and why there are two sets
NIH ODS (Iron fact sheet, updated September 4, 2025) prints one line for everyone from age 10: 12 g/dL, and 11 g/dL for younger children. The WHO’s 2024 guideline prints a line for each age, sex and trimester, set at the 5th percentile of healthy people — in its words, “The 5th percentile implies that 95% of healthy individuals would have a higher haemoglobin value, and 5% of healthy individuals would still have a lower haemoglobin value than the cutoff and be falsely diagnosed as anaemic.” The two disagree for men (12 against 13 g/dL) and in pregnancy (12 against 10.5–11 g/dL), so a result between them is shown with both, each named. The WHO’s table covers 6 months to 65 years and prints no line for older adults.
| Group | WHO: anaemia under | WHO “mild” | WHO “moderate” | WHO “severe” | NIH ODS: under |
|---|---|---|---|---|---|
| Woman 15–65, not pregnant | 120 | 110–119 | 80–109 | under 80 | 12 g/dL |
| Man 15–65 | 130 | 110–129 | 80–109 | under 80 | 12 g/dL |
| Pregnant, first trimester | 110 | 100–109 | 70–99 | under 70 | 12 g/dL |
| Pregnant, second trimester | 105 | 95–104 | 70–94 | under 70 | 12 g/dL |
| Pregnant, third trimester | 110 | 100–109 | 70–99 | under 70 | 12 g/dL |
| Girl 12–14, not pregnant | 120 | 110–119 | 80–109 | under 80 | 12 g/dL |
| Boy 12–14 | 120 | 110–119 | 80–109 | under 80 | 12 g/dL |
| Child 10–11 | 115 | 110–114 | 80–109 | under 80 | 12 g/dL |
| Child 5–9 | 115 | 110–114 | 80–109 | under 80 | 11 g/dL |
| Child 2–4 (24–59 months) | 110 | 100–109 | 70–99 | under 70 | 11 g/dL |
| Child 6–23 months | 105 | 95–104 | 70–94 | under 70 | 11 g/dL |
Over 65, the WHO prints no line: its guideline lists “men and women aged >65 years” among the groups future studies still need to measure. The checker uses NIH ODS’s 12 g/dL there, and says so. MedlinePlus prints 13.8 to 17.2 g/dL (male) and 12.1 to 15.1 g/dL (female) as normal results for adults, and adds: “Normal value ranges may vary slightly among different laboratories.”
Altitude and smoking: the WHO’s corrections
Living higher up and smoking both raise hemoglobin, so the WHO takes an amount off the result before comparing it with its line: “Adjustments are the amount subtracted from an individual’s observed haemoglobin level or added to the haemoglobin cutoff defining anaemia (in g/L).” The checker uses its tables as printed.
| Where you live, or how much you smoke | Subtract |
|---|---|
| Under 500 m | 0 |
| 500–999 m | 4 |
| 1,000–1,499 m | 8 |
| 1,500–1,999 m | 11 |
| 2,000–2,499 m | 14 |
| 2,500–2,999 m | 18 |
| 3,000–3,499 m | 21 |
| 3,500–3,999 m | 25 |
| 4,000–4,499 m | 29 |
| 4,500–4,999 m | 33 |
| Smoker, number not known | 3 |
| Under 10 a day | 3 |
| 10 to 19 a day | 5 |
| More than 20 a day | 6 |
The WHO does not adjust for infection or inflammation: “Haemoglobin concentrations should not be adjusted to diagnose anaemia in individuals and populations to account for the effect of infection and inflammation on haemoglobin concentrations.” NIH ODS and MedlinePlus print no adjustment at all, so the checker reads your number as measured against their lines.
Common results, and where they sit
| Hemoglobin | Where it sits |
|---|---|
| 9 g/dL | Under both sources’ lines |
| 11 g/dL | Under both sources’ lines |
| 11.9 g/dL | Under both sources’ lines |
| 12 g/dL | Not under either source’s line |
| 13.5 g/dL | Not under either source’s line |
| 15.1 g/dL | Not under either source’s line |
| 15.5 g/dL | Above the range MedlinePlus prints |
Worked examples
- 12.5 g/dL, a man: under the WHO’s 130 g/L line, in the band it calls “mild anaemia” (110–129 g/L), but not under NIH ODS’s 12 g/dL. The two sources disagree, and the page says so rather than choosing one.
- 11.5 g/dL, second trimester: under NIH ODS’s 12 g/dL, but not under the WHO’s 105 g/L for the second trimester — the one group the WHO sets lowest.
- 12.4 g/dL, a woman living at 1,700 m: the WHO subtracts 11 g/L for her altitude, so it reads 113 g/L against its 120 line — under it, in its “mild anaemia” band — while ODS reads the 12.4 as measured.
- 12 g/dL, a woman: exactly on both lines (“lower than 12” and “<120” leave 12 itself above), yet just under MedlinePlus’s 12.1 g/dL. Labs differ by that much.
Common mistakes
- Mixing up g/dL and g/L. 12 g/dL is 120 g/L. A US report prints the first, a UK or European one the second; the checker refuses a number that only makes sense in the other unit.
- Reading hemoglobin on its own. NIH ODS: “Hemoglobin and hematocrit tests are the most commonly used measures to screen patients for iron deficiency, even though they are neither sensitive nor specific.” And: “Often, hemoglobin concentrations are combined with serum ferritin measurements to identify IDA.”
- Taking a normal hemoglobin to mean normal iron. ODS describes a stage of iron deficiency in which iron stores are depleted “but hemoglobin levels are usually within the normal range”. That is what a ferritin test is for.
- Starting iron because of one number. Low hemoglobin has causes other than iron, and MedlinePlus is plain about it: “The test can’t tell you what’s causing an abnormal level.” Whether to take anything is your doctor’s call.
Frequently asked questions
What are normal hemoglobin levels?
MedlinePlus lists 13.8 to 17.2 g/dL for adult males and 12.1 to 15.1 g/dL for adult females as normal results, and says ranges “may vary slightly among different laboratories”. The WHO’s anaemia line is 130 g/L (13 g/dL) for men and 120 g/L for women; NIH ODS’s is 12 g/dL from age 10.
What is a normal hemoglobin level for a woman?
MedlinePlus lists 12.1 to 15.1 g/dL for adult females. The WHO’s 2024 line for women who are not pregnant is 120 g/L (12 g/dL), and NIH ODS’s line is the same 12 g/dL. In pregnancy the WHO’s line drops to 110 g/L in the first and third trimesters and 105 g/L in the second.
What is the hemoglobin normal range by age?
The WHO’s lines by age are 105 g/L at 6–23 months, 110 g/L at 24–59 months, 115 g/L at 5–11 years and 120 g/L at 12–14 years; from 15 they split by sex. NIH ODS uses 11 g/dL under 10 and 12 g/dL from 10. The WHO prints no line over 65.
What hemoglobin level is too low?
The WHO calls a result under its line “anaemia”, and splits it into “mild”, “moderate” and “severe” bands — for a woman who is not pregnant, 110–119, 80–109 and under 80 g/L. NIH ODS says values under 12 g/dL from age 10 “suggest IDA”. A result under either line is one to take to your doctor.
Is g/dL the same as g/L?
No: 1 g/dL is 10 g/L, so 12 g/dL is 120 g/L. In mmol/L, the WHO’s own guideline writes “10 g/L (0.62 mmol/L)”, so 120 g/L is about 7.4 mmol/L.
Why does altitude change hemoglobin?
Living higher up raises hemoglobin, and MedlinePlus notes that “Living at a higher altitude can also cause a high hemoglobin level.” The WHO subtracts 4 g/L from 500 m up to 33 g/L at 4,500–4,999 m before comparing a result with its line.
What does a high hemoglobin level mean?
The WHO prints no upper line. MedlinePlus’s common range tops out at 17.2 g/dL for males and 15.1 g/dL for females, it names altitude as a cause of a high result, and lists smoking and dehydration among the factors that can affect one. A high result is a question for your doctor.
Read next
- How to get rid of anemia? The best 4 products
- The best vitamins for women at 30+
- Vitamin B12 as a nootropic — the other vitamin a blood count is read with.
- Mind Lab Pro for women: what actually changes
- The Ferritin Level Checker — the iron-stores test ODS reads with hemoglobin, and the Vitamin & Mineral Dose Lookup for iron’s RDA and upper limit.
- The TIBC Level Checker — the iron panel’s binding capacity, and the saturation it gives with your serum iron.
This is not medical advice, and nothing here diagnoses or treats anything. It shows where a number sits against published lines; what it means for you is a conversation with your doctor, who knows your other results and your history. Some links on this site are affiliate links: I buy what I review at full price, and a commission never changes a verdict.