On this page
- How to use this normal lab values chart
- How reference ranges are made
- Reading your lab report step by step
- Common test panels
- US and SI units in the chart
- Ranges by age and sex
- Factors that affect lab results
- Results just outside the range
- Biotin and other interferences
- Direct-to-consumer testing
- Critical values
- When to see a doctor
- Frequently asked questions
How to use this normal lab values chart
The chart above lists typical adult reference ranges for common blood tests in both US conventional units (such as mg/dL) and SI units (such as mmol/L). Type a test name in the search box to filter it, and select any test to open its converter, which includes a full conversion chart, ranges by age and sex where relevant, and an explanation of what high and low values can mean.
Three points are worth keeping in mind:
- Your own lab report is the authority. Every laboratory sets its own reference ranges based on its equipment, methods and population. The values in this chart are typical, not universal.
- "Normal" is a statistical idea. A reference range usually covers the middle 95% of results from healthy people. That means about 1 in 20 healthy people will have a result just outside the range for any single test.
- Context matters. Age, sex, pregnancy, time of day, fasting, recent exercise, medicines and other health conditions can all change results.
This guide explains how reference ranges are created, how to read the main blood test panels, which factors change results, and when an abnormal value needs attention.
How reference ranges are made
Laboratories establish reference ranges by testing a group of healthy volunteers – ideally at least 120 people, according to Clinical and Laboratory Standards Institute (CLSI) guidance – and calculating the values between which the central 95% of results fall (the 2.5th to 97.5th percentiles). Because building a new range is expensive, many laboratories instead verify a range published by the test manufacturer or another laboratory using a smaller group of local samples.
Why ranges differ between laboratories
- Different analysers and reagents can give systematically different results for the same sample.
- Different populations – for example, by age, ethnicity, altitude or diet – have different typical values.
- Different methods – for example, immunoassays for hormones vary considerably between manufacturers.
- Rounding and reporting conventions differ.
For some tests, ranges are not based on the healthy population but on clinical decision limits – thresholds linked to outcomes. Examples include glucose and HbA1c (diabetes thresholds), cholesterol (cardiovascular risk categories) and vitamin D (sufficiency thresholds). These limits are set by expert guidelines rather than population percentiles.
The problem with "multiple tests"
Because each test has a 5% chance of being outside its range in a healthy person, ordering many tests at once makes at least one "abnormal" result likely. With 20 independent tests, the chance that all are within range is only about 36%. This is why mildly abnormal results are often repeated or interpreted in context rather than acted on immediately.
Reading your lab report step by step
- Check the details. Confirm your name, date of birth and the date and time the sample was taken. Note whether the sample was fasting if that matters for the test.
- Find the units. Each result has a unit beside it. Make sure you compare a result with a range in the same unit.
- Compare with the reference range on the report. Flags such as H (high) and L (low) highlight results outside it.
- Look at the size of the difference. A potassium of 5.2 mmol/L when the upper limit is 5.0 is very different from a potassium of 6.8.
- Look at related tests together. Creatinine with eGFR; iron with ferritin and transferrin saturation; TSH with free T4.
- Compare with previous results. A change over time is often more informative than a single value.
- Write down questions for your clinician rather than drawing conclusions from one number.
Common test panels
Basic metabolic panel (BMP) and electrolytes
| Test | US units | SI units |
|---|---|---|
| Sodium | 135–145 mEq/L | 135–145 mmol/L |
| Potassium | 3.5–5.0 mEq/L | 3.5–5.0 mmol/L |
| Chloride | 98–107 mEq/L | 98–107 mmol/L |
| Bicarbonate (CO₂) | 22–29 mEq/L | 22–29 mmol/L |
| Glucose (fasting) | 70–99 mg/dL | 3.9–5.5 mmol/L |
| BUN / urea | 7–20 mg/dL BUN | 2.5–7.1 mmol/L urea |
| Creatinine (men) | 0.7–1.3 mg/dL | 62–115 µmol/L |
| Creatinine (women) | 0.6–1.1 mg/dL | 53–97 µmol/L |
| Calcium | 8.6–10.3 mg/dL | 2.15–2.58 mmol/L |
The BMP assesses kidney function, fluid and electrolyte balance, and blood sugar. eGFR is usually reported alongside creatinine.
Comprehensive metabolic panel (CMP) additions
| Test | US units | SI units |
|---|---|---|
| Albumin | 3.5–5.0 g/dL | 35–50 g/L |
| Total protein | 6.0–8.3 g/dL | 60–83 g/L |
| Total bilirubin | 0.1–1.2 mg/dL | 2–21 µmol/L |
| ALT | about 7–56 U/L (lab-dependent) | same |
| AST | about 10–40 U/L | same |
| Alkaline phosphatase | about 44–147 U/L | same |
Liver enzyme ranges vary widely between laboratories. The American College of Gastroenterology suggests lower "healthy" ALT upper limits of about 29–33 U/L for men and 19–25 U/L for women.
Lipid panel
| Test | Desirable (US) | Desirable (SI) |
|---|---|---|
| Total cholesterol | below 200 mg/dL | below 5.2 mmol/L |
| LDL cholesterol | below 100 mg/dL | below 2.6 mmol/L |
| HDL cholesterol | above 40 (men), 50 (women) mg/dL | above 1.0 (men), 1.3 (women) mmol/L |
| Triglycerides | below 150 mg/dL | below 1.7 mmol/L |
| Non-HDL cholesterol | below 130 mg/dL | below 3.4 mmol/L |
These are decision limits rather than population ranges, and personal targets depend on cardiovascular risk. See our LDL calculator and non-HDL cholesterol calculator.
Diabetes tests
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting glucose | below 100 mg/dL (5.6 mmol/L) | 100–125 mg/dL (5.6–6.9 mmol/L) | 126 mg/dL (7.0 mmol/L) or higher |
| HbA1c | below 5.7% (39 mmol/mol) | 5.7–6.4% (39–46 mmol/mol) | 6.5% (48 mmol/mol) or higher |
| 2-hour OGTT | below 140 mg/dL (7.8 mmol/L) | 140–199 mg/dL (7.8–11.0 mmol/L) | 200 mg/dL (11.1 mmol/L) or higher |
For a full A1C chart with average glucose, see our A1C calculator and chart.
Complete blood count (CBC)
| Test | Typical adult range |
|---|---|
| Haemoglobin (men) | 13.5–17.5 g/dL (135–175 g/L) |
| Haemoglobin (women) | 12.0–15.5 g/dL (120–155 g/L) |
| White blood cells | 4.0–11.0 × 10⁹/L |
| Platelets | 150–400 × 10⁹/L |
| Mean cell volume (MCV) | 80–100 fL |
Thyroid tests
| Test | US units | SI units |
|---|---|---|
| TSH | about 0.4–4.0 mIU/L | same |
| Free T4 | about 0.8–1.8 ng/dL | about 10–23 pmol/L |
| Free T3 | about 2.3–4.2 pg/mL | about 3.5–6.5 pmol/L |
Vitamins and iron
| Test | US units | SI units |
|---|---|---|
| 25-hydroxyvitamin D | 20–50 ng/mL adequate | 50–125 nmol/L |
| Vitamin B12 | about 200–900 pg/mL | about 148–664 pmol/L |
| Folate (serum) | above about 3–4 ng/mL | above about 7–10 nmol/L |
| Ferritin (men) | about 30–400 ng/mL | 30–400 µg/L |
| Ferritin (women) | about 15–150 ng/mL | 15–150 µg/L |
| Serum iron | 60–170 µg/dL | 10.7–30.4 µmol/L |
| Transferrin saturation | 20–45% | same |
US and SI units in the chart
Each row shows a range in both unit systems. If your report uses mg/dL, read the US column; if it uses mmol/L or µmol/L, read the SI column. Converting a single value is easy with each test's converter, but remember that converting your result and then comparing it with a range from a different laboratory can be misleading. Where your report gives a range, use that range. If you have moved between countries, our lab values converter and mg/dL to mmol/L guide explain the factors used for each test and the most common mistakes, such as confusing BUN with urea or cholesterol with triglycerides.
Ranges by age and sex
Many tests have different ranges for men and women, and some change markedly with age:
| Test | How it varies |
|---|---|
| Creatinine | Higher in men (more muscle mass); lower in children and older adults with low muscle mass |
| Haemoglobin and ferritin | Higher in men; ferritin in women rises after menopause |
| Testosterone and estradiol | Very different by sex; change across puberty, the menstrual cycle, menopause and ageing |
| Alkaline phosphatase | Much higher in growing children and adolescents |
| Phosphate | Higher in children |
| Uric acid | Higher in men; rises in women after menopause |
| HbA1c | Rises slightly with age, by about 0.1 percentage point per decade |
| eGFR | Falls gradually with age |
| Cholesterol | Rises with age; rises in women after menopause |
The chart above shows adult ranges. For children, use the paediatric ranges supplied by the testing laboratory.
Pregnancy
Pregnancy changes many results: haemoglobin, albumin, creatinine, urea and sodium fall; cholesterol, triglycerides, alkaline phosphatase and some clotting factors rise; and thyroid hormone ranges shift, particularly in the first trimester. Trimester-specific ranges should be used where available.
Factors that affect lab results
- Fasting: glucose and triglycerides rise after meals; most other tests change little.
- Time of day: cortisol, testosterone and iron are highest in the morning.
- Exercise: strenuous activity raises creatine kinase, AST, creatinine and sometimes potassium.
- Hydration: dehydration concentrates albumin, haemoglobin, urea and creatinine.
- Posture and tourniquet: standing and prolonged tourniquet time raise protein-bound substances.
- Medicines and supplements: biotin interferes with many immunoassays (thyroid, troponin, hormones); diuretics alter electrolytes; steroids raise glucose.
- Sample handling: delayed processing raises potassium and lowers glucose; haemolysis raises potassium and AST.
- Menstrual cycle: sex hormones vary dramatically by cycle phase.
- Ethnicity: some ranges, such as for white cell counts (lower in people with the Duffy-null phenotype, common in people of African ancestry) and creatine kinase, differ between populations.
Results just outside the range
Mildly abnormal results are very common and are often not significant. Clinicians typically consider:
- How far outside the range the result is. Small deviations are often within the test's normal variation.
- Whether there is a plausible explanation, such as recent exercise, a meal, dehydration, a new medicine or a minor illness.
- Whether other results fit the same pattern. A slightly high ALT with normal other liver tests is less concerning than a pattern of abnormal results.
- Symptoms and medical history.
- Whether the result has changed. A creatinine that has crept up over several tests matters more than a single high value.
A common approach is to repeat the test after a few weeks, under standardised conditions, before investigating further.
Biological variation
Every test result varies from day to day even in a healthy person. This biological variation differs between tests: sodium is tightly controlled and varies by less than 1%, whereas triglycerides can vary by 20% or more and serum iron by 30% or more. When comparing two results, clinicians consider the reference change value – the difference needed before a change is likely to be real rather than random. For creatinine, a change of about 15–20% is generally needed; for cholesterol, about 10–15%.
Biotin and other interferences
High-dose biotin (vitamin B7) supplements, often taken for hair, skin and nails, can interfere with immunoassays that use biotin–streptavidin technology. Depending on the assay design, biotin can cause falsely high or falsely low results for thyroid tests, troponin (used to diagnose heart attacks), sex hormones, vitamin D and others. The US Food and Drug Administration has issued safety communications about this. If you take biotin, tell your clinician, and consider stopping it for at least 48 hours before blood tests, or longer for high doses, if your clinician agrees.
Other interferences include:
- Heterophile antibodies, which can affect hormone and tumour marker tests
- Macroprolactin and macro-CK, which raise results without clinical significance
- Lipaemia (very fatty samples) and icterus (very high bilirubin), which affect several chemistry tests
Direct-to-consumer testing
Many people now order blood tests online without a doctor's referral. These tests can be convenient, but some caution is wise:
- Choose an accredited laboratory (for example, CLIA-certified in the US or UKAS-accredited in the UK).
- Expect some results to be slightly outside the range by chance, particularly with large panels.
- Be aware that results may not be interpreted in the context of your health, and that follow-up may be needed with your own clinician.
- Avoid repeated testing of the same markers at short intervals unless advised; random variation can be mistaken for real change.
Critical values
Some results are so abnormal that the laboratory telephones the clinician immediately. Thresholds vary, but typical critical values include:
| Test | Critical low | Critical high |
|---|---|---|
| Glucose | below 40–50 mg/dL (2.2–2.8 mmol/L) | above 400–500 mg/dL (22–28 mmol/L) |
| Potassium | below 2.5–2.8 mmol/L | above 6.0–6.5 mmol/L |
| Sodium | below 120 mmol/L | above 155–160 mmol/L |
| Calcium | below 6.5–7.0 mg/dL (1.6–1.75 mmol/L) | above 13 mg/dL (3.25 mmol/L) |
| Haemoglobin | below 6–7 g/dL (60–70 g/L) | – |
| Platelets | below 20–50 × 10⁹/L | above 1,000 × 10⁹/L |
These values require urgent clinical assessment.
When to see a doctor
Discuss any result outside the reference range with your clinician, especially if it is markedly abnormal, has changed since a previous test, or is accompanied by symptoms. Many slightly abnormal results are not significant and simply need repeating. Seek urgent care for critical values or for symptoms such as chest pain, severe weakness, confusion, fainting, shortness of breath or signs of bleeding.
Frequently asked questions
Why is my result flagged when my doctor isn't worried?
Because 5% of healthy people fall slightly outside a typical range, and context – your history, symptoms and other results – determines significance.
Are these ranges the same for children?
No. This chart lists adult values. Children have different ranges for many tests, including creatinine, phosphate and alkaline phosphatase.
Why does my lab use a different range from this chart?
Ranges depend on the laboratory's equipment, methods and population. Always use the range printed on your report.
Can I be unwell with "normal" results?
Yes. A normal result does not rule out disease, and some conditions only show in specific tests or over time.
Do I need to fast for blood tests?
Only for some, such as fasting glucose or certain lipid tests. Follow the instructions given with your test.
What does "H" or "L" on my report mean?
They indicate results above (high) or below (low) the laboratory's reference range. Some reports also use "HH" or "LL" or an asterisk for critical values.
How often should I have routine blood tests?
It depends on your age, health and medicines. Healthy adults may need only occasional tests, such as cholesterol every few years and diabetes screening based on risk. People with long-term conditions or on certain medicines need regular monitoring.
Can stress affect blood test results?
Acute stress can raise glucose, cortisol, white cell counts and, briefly, some hormones such as prolactin. A calm, routine visit for testing gives the most representative results.
Should I stop my medicines before a blood test?
Not unless your clinician tells you to. Some tests, such as drug levels or thyroid tests, are timed in relation to doses, so ask if you are unsure.
Why are some results reported as "less than" a number?
When a result is below the lowest level the test can reliably measure, the laboratory reports it as "less than" that limit – for example, "<0.5". This usually means the level is very low or undetectable.
Are reference ranges different at high altitude?
Yes, for some tests. People living at high altitude have higher haemoglobin and haematocrit because the body makes more red cells in response to lower oxygen levels. Laboratories in high-altitude regions often use adjusted ranges, and the World Health Organization provides altitude adjustments for haemoglobin when assessing anaemia.
Is a result at the edge of the range a warning sign?
Usually not on its own. A result near the upper or lower limit is still within the range that most healthy people fall into. Trends over time and other results are more informative than a single borderline value.