What Do the Numbers on Your Blood Test Report Actually Mean?
Every number on a blood test report is a measurement of how much of something is in your blood, expressed in a specific unit, and compared against a reference range that the lab expects for healthy people like you. The number only makes sense with its unit and its range. "5.4" means nothing on its own. "HbA1c 5.4%, range below 5.7%" tells you your average blood sugar over the last three months is in the normal range.
This guide decodes every part of a result row: the units, the flags, the symbols, and the confusing formats like "<0.5" or "1:80".
The Anatomy of a Result Row
A typical row on an Indian lab report looks like this:
| Test | Result | Flag | Unit | Biological reference interval | Method |
|---|---|---|---|---|---|
| Fasting Blood Sugar | 112 | H | mg/dL | 70 - 99 | Hexokinase |
- Test: what was measured
- Result: your value
- Flag: H (high) or L (low) if outside the range, blank if within it
- Unit: how the value is measured
- Biological reference interval: the range the lab expects for healthy people of your age and sex
- Method: how the lab measured it, which matters when comparing labs
What the Units Mean
Units tell you how much of something is in a given amount of blood. These are the ones you will see most often on Indian reports.
| Unit | Read as | Measures | Common tests |
|---|---|---|---|
| g/dL | grams per decilitre | Weight in 100 mL of blood | Haemoglobin, albumin, total protein |
| mg/dL | milligrams per decilitre | Smaller weight in 100 mL | Glucose, cholesterol, creatinine, urea, uric acid, calcium |
| mmol/L | millimoles per litre | Number of molecules in 1 L | Sodium, potassium, sometimes glucose and cholesterol |
| U/L or IU/L | units per litre | Enzyme activity | SGPT (ALT), SGOT (AST), ALP, GGT |
| ng/mL | nanograms per millilitre | Very small amounts | Vitamin D, ferritin, PSA |
| pg/mL | picograms per millilitre | Even smaller amounts | Vitamin B12 |
| µIU/mL or mIU/L | micro or milli international units | Hormone activity | TSH, insulin |
| % | percentage | Proportion | HbA1c, haematocrit, differential WBC count |
| cells/µL or /cumm | cells per microlitre | Cell count | WBC, platelets |
| lakhs/cumm | lakhs per cubic millimetre | Cell count in Indian notation | Platelets (for example 2.5 lakhs) |
| million/µL | millions per microlitre | Cell count | RBC |
| fL | femtolitres | Cell size | MCV |
| mL/min/1.73m² | millilitres per minute, adjusted for body size | Filtering rate | eGFR |
mg/dL vs mmol/L: why the same test can look so different
Some labs, and most reports from abroad, use mmol/L instead of mg/dL. The same fasting glucose can appear as 99 mg/dL or 5.5 mmol/L. Both are normal. Comparing across units without converting is a common mistake.
| Test | Convert mmol/L to mg/dL |
|---|---|
| Glucose | Multiply by 18 |
| Total cholesterol, LDL, HDL | Multiply by 38.67 |
| Triglycerides | Multiply by 88.57 |
| Creatinine (µmol/L) | Divide by 88.4 |
Platelet counts in lakhs
Indian reports often show platelets as "2.5 lakhs/cumm", which is 2,50,000 per microlitre. Another lab may print "250 x 10³/µL". These are the same number.
What the Flags and Symbols Mean
| Symbol | Meaning |
|---|---|
| H, High, ↑ | Above the reference range |
| L, Low, ↓ | Below the reference range |
| Bold or red text | Outside the range, highlighted by the lab |
| * or ** | Outside the range, or a footnote about the method. Check the bottom of the page |
| C, Critical, Panic value | Far outside the range; labs often call the doctor directly |
| Blank | Within the range |
A flag tells you which side of the range you are on, not how far. Always look at the number itself to see whether it is just past the limit or far beyond it.
Unusual Result Formats
Less than or greater than (<, >)
"CRP <0.5 mg/L" means the value was below the lowest level the lab's machine can measure. This is usually good news: there is so little that it could not be detected precisely.
"Vitamin B12 >2000 pg/mL" means the value was above the highest level the machine measures. Very high B12 is often due to recent supplements or injections.
Ratios
Some results are ratios, like "Total Cholesterol/HDL Ratio 4.2" or "BUN/Creatinine Ratio 15". Ratios have no unit because they divide one value by another. Lower cholesterol ratios are generally better.
Titres (1:80, 1:160)
Tests like Widal (typhoid) and ANA report results as dilutions. "1:160" means the antibody was still detected after diluting your blood 160 times. Higher second numbers mean more antibody. Titres are hard to read without context and are best discussed with a doctor.
Positive, negative, reactive, non-reactive
Some tests are qualitative, not numeric. "Non-reactive" and "Negative" mean the substance was not detected. "Reactive" or "Positive" means it was, and usually needs a confirmatory test.
Calculated values
Values like LDL, VLDL, eGFR and globulin are often calculated from other results rather than measured directly. The report may say "Calculated" in the Method column. They are still useful, but depend on the accuracy of the values they are calculated from.
What the Reference Range Really Means
The reference range is the band of values that about 95 percent of healthy people fall within. Three things follow from this:
- About 5 percent of healthy people fall outside it for any single test, so a mild flag is not automatically a problem.
- Being inside it is not a guarantee of health. A value at the very edge may still be worth watching.
- It is specific to the lab, and often to your age and sex. Always use the range on your own report.
Some tests use decision limits instead of a normal range. HbA1c, for example, uses cutoffs: below 5.7% normal, 5.7 to 6.4% prediabetes, 6.5% and above diabetes. LDL uses targets that depend on your heart risk.
Reading Your Numbers Faster
Decoding units, flags and ranges for 60 values takes time. ReportSense does this for every row automatically: it reads the value and unit from your PDF, checks that the number is plausible (so a 4.2 misread as 42 is caught and you are asked to confirm it), compares it against the right range for your age and sex, and explains what it means in plain language.
Frequently Asked Questions
What does H and L mean on a blood test?
H means your value is higher than the reference range and L means it is lower. The flag does not show how far outside the range you are, so always check the actual number.
What does an asterisk mean on a lab report?
It usually marks a value outside the range, or points to a footnote about the method or sample. Check the bottom of the page for the explanation.
What does "<" mean in a blood test result?
It means your value was below the lowest amount the lab can measure. For markers like CRP, this is usually a good sign.
Why does my glucose look different on a foreign report?
Many countries report glucose in mmol/L. Multiply by 18 to convert to mg/dL. For example, 6.0 mmol/L is about 108 mg/dL.
What is a biological reference interval?
It is another name for the reference range: the values seen in about 95 percent of healthy people of a similar age and sex, as determined by that lab.
The Takeaway
A number on your report only means something with its unit and its range. Learn the common units, read flags as direction rather than severity, watch for unusual formats like "<" and ratios, and always compare with the range printed on your own report.
Must Read
- How to Read a Blood Test Report Without Googling Every Number - A simple four-question method for any report
- Blood Test Normal Ranges Chart for Indian Adults (2024) - Typical ranges for every major panel
Try ReportSense to understand your report. ReportSense reads every value, unit and flag on your report, checks each number is plausible, and explains what it means for your age and sex in plain language. Try it free at reportsense.in.
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