Lipase Unit Converter
Lipase Unit Converter
Convert serum lipase between U/L, IU/L, µkat/L and nkat/L, with the three-times-upper-limit diagnostic threshold and why the height of the rise says nothing about severity.
Lipase converter
Activity unitsSerum lipase 35 U/L
Formula and conversion factor
U/L = µkat/L × 60
nkat/L = U/L × 16.667
- U
- 1 unit = 1 µmol of substrate hydrolysed per minute
- kat
- 1 katal = 1 mol per second, so 1 U/L = 1/60 µkat/L; IU/L is numerically identical to U/L
- 3 × ULN
- the revised Atlanta biochemical criterion for acute pancreatitis — three times the reporting laboratory's own upper limit, which is 180 U/L against a 60 U/L limit
- method dependence
- lipase methods differ in substrate and in whether colipase is added, so the upper limit and therefore the threshold differ between laboratories
Worked example
Serum lipase 35 U/L
35 ÷ 60 = 0.583 µkat/L
= 583 nkat/L = 35 IU/L
Within the adult reference interval of 13–60 U/L, and well below the 180 U/L diagnostic threshold
Reference interval and the diagnostic threshold
| U/L | µkat/L | |
|---|---|---|
| Adult reference interval | 13 – 60 | 0.217 – 1.000 |
| Above the interval — not by itself diagnostic | > 60 | > 1.000 |
| Revised Atlanta threshold, three times this upper limit | ≥ 180 | ≥ 3.000 |
Lipase against amylase in suspected pancreatitis
| Lipase | Amylase | |
|---|---|---|
| Rises after onset | 4 – 8 hours | 2 – 12 hours |
| Returns to normal | 8 – 14 days | 3 – 5 days |
| Useful in a late presentation | Yes | No |
| Raised by salivary disease | No | Yes |
| Sensitivity in alcohol-related pancreatitis | Higher | Lower |
| Recommended first-line by current guidelines | Yes | Only where lipase is unavailable |
A threshold that belongs to your laboratory, not to the number
Lipase is reported as catalytic activity in U/L or the numerically identical IU/L, and in µkat/L or nkat/L in SI-strict laboratories. A unit is one micromole of substrate hydrolysed per minute and a katal is one mole per second, so the conversion is a division by 60 and nothing more: a lipase of 35 U/L is 0.583 µkat/L. Because the result is an activity rather than a concentration of protein, no molar unit exists.
Lipase has largely displaced amylase as the first-line test for acute pancreatitis, for two reasons. It is more specific to the pancreas — the salivary glands make an amylase isoenzyme but not lipase, so parotitis does not raise it — and it stays elevated far longer, for eight to fourteen days against three to five for amylase. That longer window is what matters clinically, because patients frequently present two or three days into an attack, by which time amylase may have returned to normal. Sensitivity is also better in alcohol-related disease. Measuring both enzymes together adds very little and simply costs more.
The diagnostic threshold is the part most often got wrong. The revised Atlanta classification requires a lipase or amylase of at least three times the upper limit of normal, together with characteristic pain or characteristic imaging — two of those three features make the diagnosis. Crucially, the threshold is three times the reporting laboratory’s own upper limit, not a fixed number: against an upper limit of 60 U/L it is 180 U/L, but against 80 U/L it is 240 U/L. A lipase merely above the reference interval is not, on its own, acute pancreatitis.
Two further cautions. A raised lipase is not exclusive to the pancreas: renal impairment reduces clearance and lifts it, and bowel obstruction, perforation, mesenteric ischaemia, diabetic ketoacidosis and several drugs will raise it too. And the magnitude of the rise carries no prognostic information whatever. Severity is graded on organ failure and local complications using the revised Atlanta criteria and physiological scores, so following the lipase serially through an admission adds nothing.
Frequently asked questions
How do I convert lipase from U/L to µkat/L?
Divide by 60. A unit is one micromole of substrate hydrolysed per minute and a katal is one mole per second. A lipase of 35 U/L is 0.583 µkat/L, or 583 nkat/L, and IU/L is the same number as U/L.
What lipase level diagnoses acute pancreatitis?
At least three times the upper limit of normal, alongside characteristic pain or characteristic imaging — two of those three features are required by the revised Atlanta classification. The threshold is three times your own laboratory’s limit, so it is 180 U/L against a limit of 60 but 240 U/L against a limit of 80.
Is lipase better than amylase?
For acute pancreatitis, yes. It is more specific to the pancreas, more sensitive in alcohol-related disease, and stays raised for eight to fourteen days rather than three to five, so it is still abnormal in a patient who presents late. Measuring both adds little.
Does a very high lipase mean a severe attack?
No. The magnitude of the rise carries no prognostic information. Severity is graded on organ failure and local complications under the revised Atlanta criteria, and following the lipase serially through an admission does not help.
What raises lipase apart from pancreatitis?
Renal impairment, which reduces clearance, is the commonest. Bowel obstruction, perforation and mesenteric ischaemia, diabetic ketoacidosis, and several drugs will also raise it, so a modestly elevated lipase in the wrong clinical context should not be taken as pancreatitis.
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References
- Banks PA, Bollen TL, Dervenis C, et al. Classification of acute pancreatitis — 2012: revision of the Atlanta classification and definitions by international consensus. Gut. 2013;62(1):102–111.
- Working Group IAP/APA Acute Pancreatitis Guidelines. IAP/APA evidence-based guidelines for the management of acute pancreatitis. Pancreatology. 2013;13(4 Suppl 2):e1–e15.
- Ismail OZ, Bhayana V. Lipase or amylase for the diagnosis of acute pancreatitis? Clin Biochem. 2017;50(18):1275–1280.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.