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Read this before the chart
This blood test results chart gives the usual adult ranges for the lines a routine report most often carries: the blood count, glucose and HbA1c, kidney and liver lines, TSH, ferritin and LDL cholesterol. Use it as a reading aid, not a verdict: the range that applies to your value is the one printed beside it on your own report.
Most tests have no national standard range. Each laboratory sets or checks its own, because the figure depends on the analyzer, the reagents, the calibration, the method and the people that laboratory serves. Two laboratories twenty minutes apart can print different ceilings for ferritin or TSH and both be right.
The gaps are not a rounding detail. A 2025 review in the Journal of the American Board of Family Medicine notes that only three common tests are harmonised across methods (cholesterol, creatinine and HbA1c), and that hemoglobin measured on a blood gas analyzer can read 0.5 to 1.0 g/dL higher than the same blood run in the main laboratory.
How a laboratory builds a range
To set a range, a laboratory measures at least 120 healthy people for a given age group, sex and method, and keeps the band where most of their results fall. About one healthy person in twenty lands outside that band on any single test. Those people are not ill; they sit at the edges.
That has a consequence nobody warns you about. On a panel of 20 tests, the same review calculates that roughly two healthy people in three will have at least one result marked high or low. A flag somewhere on a long report is closer to the rule than the exception, and a longer panel produces more of them.
The labeling matters because laboratory results drive about 70% of clinical decisions, the review estimates, and because minor variations labeled high or low cause patients worry it calls unwarranted. The flag is doing its job: it says the value sits at the edge of what the laboratory saw in healthy people, and nothing more.
Complete blood count
Adult values. Units vary between laboratories: 10⁹/L and 10³/µL are the same figure, while g/dL and g/L differ by a factor of ten, so 13.5 g/dL and 135 g/L describe the same hemoglobin.
Hemoglobin is where sex matters most. A 2024 analysis of healthy people from eight countries, carried out to inform the World Health Organization, put the lower limit at about 12.0 g/dL for non-pregnant women and 13.5 g/dL for men, with the two sexes similar until adolescence. Many laboratories print 13.0 for men, as this chart does, which is exactly the kind of half-point gap that makes your own report the reference.
Read the count as a group rather than line by line: hemoglobin with MCV, which describes red cell size, and with ferritin; white cells with their breakdown into types; platelets with the rest. A single line just outside its band is a different situation from several lines moving together, and that difference is a fair question to put to your doctor.
Chemistry, liver, kidney
Where a target replaces a range, as it does for LDL cholesterol, the figure depends on your cardiovascular risk and is set by your clinician, not by the laboratory. US reports give most of these lines in mg/dL; reports elsewhere often use mmol/L, which is why the glucose row shows both.
Creatinine is made by muscle as well as cleared by the kidneys, so every equation that turns it into an eGFR uses stand-ins for muscle mass such as age and sex. The eGFR is a calculation, not a measurement. Since 2021, a joint task force of the National Kidney Foundation and the American Society of Nephrology has recommended that all US laboratories use an equation without a race term, with cystatin C to confirm results that matter.
ALT is the line where printed ceilings vary most. A US gastroenterology guideline puts a truly healthy ALT at 29 to 33 U/L for men and 19 to 25 U/L for women, below the ceiling many laboratories print, and advises that values above it be assessed. The same ALT can therefore be flagged by one laboratory and not by another.
Ferritin carries a trap. It reflects iron stores but also rises with inflammation, so a reassuring ferritin during an infection or an inflammatory illness can hide low iron. A Swiss expert consensus treats 30 µg/L (the same figure in ng/mL) as an accurate floor for iron deficiency only in people without inflammation.
| Test | Usual range | Notes |
|---|---|---|
| Fasting glucose | 70 – 100 mg/dL · 3.9 – 5.5 mmol/L | Fasting only. 100–125 is the pre-diabetic band. |
| HbA1c | < 5.7 % | Three-month average. No fasting needed. |
| Creatinine | 0.7 – 1.3 mg/dL (m) · 0.6 – 1.1 (f) | Depends on muscle mass. Read with eGFR. |
| eGFR | > 90 mL/min/1.73 m² | An estimate from a formula, not a measurement. |
| ALT | 10 – 45 U/L | Read with AST and GGT, never alone. |
| TSH | 0.4 – 4.0 mIU/L | Follows a daily rhythm. Prefer a morning draw. |
| Ferritin | 30 – 400 µg/L (m) · 15 – 200 (f) | Rises with inflammation, which can mask a deficiency. |
| LDL cholesterol | target, not a range | Below 3.0 mmol/L for low risk; lower targets apply above it. |
Ranges, targets and cut-offs
Not every number in a chart like this is a reference range, and mixing them up causes a lot of needless worry. Four kinds of figure appear on reports, and each answers a different question.
The pre-diabetic band in the table is a cut-off of the second kind, set by the same diabetes guidance. HbA1c needs no fasting, and since 2016 European laboratory and atherosclerosis societies have advised that a routine lipid panel does not need fasting either.
- 100–125
- Fasting glucose in mg/dL that the ADA classes as prediabetes.[3]
- 5.7–6.4 %
- HbA1c range the ADA classes as prediabetes, measured without fasting.[3]
- < 55
- LDL target in mg/dL for very-high-risk adults in the 2019 European guideline.[8]
- Reference rangeWhere most healthy people fall on that laboratory’s method. Sitting just outside it is common in healthy people.
- Diagnostic cut-offA threshold agreed by a medical society. The American Diabetes Association diagnoses diabetes from a fasting glucose of 126 mg/dL or an HbA1c of 6.5%.
- Treatment targetA goal tied to your risk. The 2019 European lipid guideline sets LDL below 116 mg/dL for low-risk adults, and lower at each step up.
- Critical valueA result so far out that US rules require the laboratory to alert the clinician who ordered the test immediately.
What shifts a range
Sex and age change several lines outright. Hemoglobin limits are similar in boys and girls until adolescence and then separate; pregnancy lowers them again, to about 11.0 g/dL in the first trimester in the 2024 analysis. Children have their own values for many lines, including several enzymes, so a child’s report should never be read against an adult chart like this one.
Two more shifts are invisible on the report. The first is method: changing laboratories in the middle of a follow-up can move a result without anything changing in you. The second is the clock. TSH is highest in the early morning, and in one large hospital data set it was up to about a quarter lower by early afternoon than at 7 am, which is why a morning draw makes results easier to compare.
Preparation is the third. European recommendations on blood sampling treat patient preparation, fasting included, as part of a valid result. If a flagged value could have been moved by a meal, the time of day or a change of laboratory, it is reasonable to ask whether it should be repeated under the same conditions.
Optimal ranges and red flags
Charts that promise optimal ranges answer a different question. A reference range describes healthy people, while some thresholds are chosen for a purpose and can differ for the same test. The family medicine review gives folate as an example: one level prevents anemia, a higher one is needed for homocysteine to normalize. Neither is your laboratory’s range, and neither should drive treatment without your clinician.
Real red flags are less about one letter than about patterns: a value far outside its range, several related lines moving the same way, a clear change from your own previous result, or an abnormal result alongside symptoms. Those are the situations to raise promptly with your doctor. For results that are dangerously far out, US rules require the laboratory to alert the ordering clinician immediately, so the most urgent findings are designed to reach a professional without depending on you.
A longer panel is not a safer one. A Cochrane review of general health checks in 251,891 adults found little or no effect on deaths, while every extra line adds one more chance of a flag to explain.
What a report could tell you
A value, a range and a flag leave you with the hardest part: deciding whether it matters. The family medicine review argues that reports should say so in plain words: no immediate concern, discuss at your next visit, or contact your doctor at your earliest convenience.
The format helps too. A 2024 systematic review of 18 studies found that showing a result as a horizontal bar against its range improved understanding, and made people less inclined to search online or contact their doctor than numbers with a range alone. Most reports still offer neither, so the useful questions fall to you.
Take four of them to your appointment: how far outside is the value, in which direction, which related lines agree with it, and how does it compare with your last result? They turn a general chart like this one into a conversation about you.