Lab units conversion, with the factor shown
Glucose, cholesterol, triglycerides, creatinine and vitamin D change number when a lab switches between mass units and molar units. These are the factors BioPanel uses, the unit spellings it treats as the same unit, and the markers it leaves alone.
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What a unit conversion is, and when it is safe
A lab result is a number and a unit, and the two travel together. The same glucose can be printed as 92 mg/dL on one report and 5.1 mmol/L on another. It is the same amount of glucose written two ways, because one unit weighs it and the other counts molecules.
A conversion is safe when there is one fixed factor between two units for one substance. Glucose in mg/dL is its value in mmol/L times 18.016, because 18.016 comes from the molar mass of glucose. It stops being safe when one name can mean different things, or when the two scales are not related by a single multiple. In those cases BioPanel keeps the printed unit and marks the marker as mixed.
A conversion changes how a value is shown, not whether it is outside its range. That is decided in the unit the report printed, against the range printed on the same report, so rounding in a converted number can never change a flag. This page is arithmetic. It does not say what any value means, and it is not medical advice.
Exact factors between mass and molar units
Read from the table the converter itself uses.
| Marker | Mass to molar | Molar to mass | Worked example |
|---|---|---|---|
| GlucoseMolar mass 180.16 g/mol. | mg/dL to mmol/L: ÷ 18.016 | mmol/L to mg/dL: × 18.016 | 100 mg/dL = 5.6 mmol/L |
| Total, LDL, HDL and non-HDL cholesterolCholesterol molar mass 386.65 g/mol. | mg/dL to mmol/L: ÷ 38.67 | mmol/L to mg/dL: × 38.67 | 200 mg/dL = 5.17 mmol/L |
| TriglyceridesTriglyceride factor based on triolein, 885.4 g/mol. | mg/dL to mmol/L: ÷ 88.57 | mmol/L to mg/dL: × 88.57 | 150 mg/dL = 1.69 mmol/L |
| CreatinineMolar mass 113.12 g/mol. | mg/dL to µmol/L: × 88.4 | µmol/L to mg/dL: ÷ 88.4 | 1 mg/dL = 88 µmol/L |
| Vitamin D, 25-hydroxyMolar mass 400.64 g/mol; ng/mL and µg/L are the same unit. | ng/mL to nmol/L: × 2.496 | nmol/L to ng/mL: ÷ 2.496 | 30 ng/mL = 75 nmol/L |
The factors come from molar mass, so a lab that rounds its own factor can differ from these in the last digit. Results are shown at the decimals labs usually print.
Spellings and scales that are the same unit
Where only the notation or a power of ten differs.
| Markers | Units | Relation |
|---|---|---|
| Hemoglobin, albumin, total protein, globulin, MCHC | g/dL, g/L | 1 g/dL is exactly 10 g/L. |
| Hematocrit | %, L/L | A fraction of 1 and a percentage differ by exactly 100. |
| White cell, platelet and differential counts (absolute) | 10^9/L, 10^3/µL, cells/µL | 10^9/L and 10^3/µL are the same number; cells/µL is 1000 times larger. |
| Red cell count | 10^12/L, 10^6/µL | 10^12/L and 10^6/µL are the same number. |
| Sodium, potassium, chloride, bicarbonate | mmol/L, mEq/L | Monovalent ions only: one mEq equals one mmol. |
| ALT, AST, GGT, ALP | U/L, IU/L | U/L and IU/L are the same unit. |
| Ferritin, PSA, IGF-1 | ng/mL, µg/L | ng/mL and µg/L are the same unit. |
| Vitamin B12 and estradiol (mass units only) | pg/mL, ng/L | pg/mL and ng/L are the same unit. pmol/L is not converted. |
| TSH, insulin, fasting insulin (mass-equivalent units only) | mIU/L, µIU/mL | mIU/L and µIU/mL are the same unit. pmol/L is not converted. |
| CRP and hs-CRP | mg/L, mg/dL | 1 mg/dL is exactly 10 mg/L. |
| Apolipoprotein B | g/L, mg/dL | 1 g/L is exactly 100 mg/dL. |
Not converted, and why
Kept in the unit the report printed.
Everything that is not in the two tables above stays in its printed unit, even where a textbook factor exists. When one marker appears in two units that cannot be converted exactly, BioPanel marks it as mixed, shows each value with its own unit, and leaves it off the line.
- HbA1c, percent and mmol/mol. The two scales are linked by a formula with an offset, not a single multiplier.
- Lp(a), mg/dL and nmol/L. The particles vary in size, so there is no single factor.
- Calcium, bilirubin and similar. Total, ionised, direct and indirect forms share a name on some reports, so one factor can be applied to the wrong form.
- BUN and urea. One counts the nitrogen in urea and the other the whole molecule, and reports do not always say which.
- Hormones, insulin and vitamins in pmol/L. Total and free forms, and different assay standards, change the relation, so only identical-unit spellings are merged, such as pg/mL and ng/L.
Try a conversion
Uses the same code and factors as the converter.
How to convert a lab value by hand
The same steps BioPanel follows for each value.
Find the marker and both units
Look the marker up in the factor table on this page. Check that the two units you have are both listed for it. If one is not, there is no exact conversion here.
Multiply or divide in the right direction
Use the factor as shown. For glucose, mg/dL divided by 18.016 gives mmol/L, and mmol/L times 18.016 gives mg/dL. For example 100 mg/dL = 5.6 mmol/L.
Round for display only
Round the result to the decimals labs normally print for that unit, and keep the printed value too. Do not feed a rounded number into further arithmetic.
Convert the range the same way
If you compare a value with a printed range in another unit, convert the range's bounds with the same factor. For flags, compare in the unit the report printed.
Keep the original unit
Write the original value and unit in their own columns beside the converted one, so any conversion can be checked later. BioPanel's long CSV does this with value_as_printed, unit_as_printed, converted and factor.
Converting by hand, with a generic PDF-to-Excel converter, or with BioPanel
What happens to units when reports from two labs meet in one sheet.
| What is compared | Spreadsheet by hand | Generic PDF-to-Excel | BioPanel |
|---|---|---|---|
| Finding the factor | Search for it each time, and find slightly different values. | Not handled. Units stay as printed. | One factor per marker, listed on this page. |
| Which direction to apply it | Easy to invert: dividing where the factor should multiply. | Not handled. | Applied by the code and shown as × or ÷ next to the value. |
| Knowing a marker should not be converted | You need to know. | Not handled. | Only markers with an exact rule are converted. Others are marked mixed. |
| Converting the printed range | Often forgotten, so the value and range sit in different units. | Range stays as text. | Range bounds are converted for display. The flag is still computed in the printed unit. |
| Keeping the original | Overwritten by the converted number. | Not applicable. | Kept in its own columns in the long CSV. |
| Same unit, different spelling | mg/dl, mg/dL and mg per dl are three cells. | Spelling stays as printed. | Spellings of the same unit are tidied to one. |
| Rounding | Whatever the cell shows, sometimes copied rounded. | Not applicable. | Rounded for display only, using the decimals labs usually print. |
| Interpretation | Yours, or your clinician's. | None. | None. Arithmetic only. |
Questions people ask
How do I convert glucose from mg/dL to mmol/L?
Divide by 18.016. 100 mg/dL = 5.6 mmol/L. To go the other way, multiply by 18.016: 5 mmol/L = 90 mg/dL. BioPanel shows the factor next to every converted value.
How do I convert cholesterol from mg/dL to mmol/L?
Divide by 38.67. 200 mg/dL = 5.17 mmol/L. The same factor is used for total, LDL, HDL and non-HDL cholesterol, because they are all cholesterol.
Why is the triglyceride factor different from the cholesterol factor?
Triglycerides are heavier molecules than cholesterol, so one mmol of them weighs more. The factor is 88.57: 150 mg/dL = 1.69 mmol/L. Using the cholesterol factor for triglycerides gives a wrong answer by more than a factor of two.
How do I convert creatinine between mg/dL and µmol/L?
Multiply mg/dL by 88.4 to get µmol/L, or divide µmol/L by 88.4 to get mg/dL. 1 mg/dL = 88 µmol/L, rounded to the whole numbers labs usually print for µmol/L.
How do I convert vitamin D between ng/mL and nmol/L?
For 25-hydroxy vitamin D, multiply ng/mL by 2.496 to get nmol/L. 30 ng/mL = 75 nmol/L. ng/mL and µg/L are the same unit, so those two need no arithmetic.
Why does BioPanel not convert HbA1c between % and mmol/mol?
The two scales are linked by a formula that has an offset as well as a multiplier, and each is tied to its own reference method. That is not a single factor, so BioPanel keeps each report's unit as printed and marks the marker as mixed rather than applying a conversion it cannot call exact.
Which markers does BioPanel leave in their printed units?
Everything without an exact rule on this page. Some have a factor in textbooks but a name that can mean different things: calcium (total or ionised), bilirubin (total, direct or indirect), BUN and urea, and hormones such as testosterone (total or free). Lp(a) has no single mass-to-molar factor. These stay as printed and are marked as mixed when units differ.
Does a converted value change a flag?
No. The flag is computed from the value and the range as the report printed them, in the unit the report used. The converted value and range are only for reading across reports. Rounding in a conversion cannot move a value in or out of range.
Why do other sources show a slightly different factor?
Many sources round: 18 for glucose, 38.6 or 39 for cholesterol, 2.5 for vitamin D. BioPanel uses the longer factors from molar mass, shown in the table, and displays results at the decimals labs print, so the difference rarely reaches the last digit shown. The factor used is always visible.
Is ng/mL the same as µg/L, and U/L the same as IU/L?
Yes to both. 1 ng/mL is 1 µg/L, and 1 U/L is 1 IU/L, so the number does not change. BioPanel treats those spellings as one unit for the markers where they are used, such as ferritin, PSA and the liver enzymes.