Amylase Unit Converter
Amylase Unit Converter
Convert serum amylase between U/L, IU/L, µkat/L and nkat/L, and see why a normal amylase does not exclude pancreatitis and a very high one does not mean a severe attack.
Amylase converter
Activity unitsSerum amylase 85 U/L
Formula and conversion factor
U/L = µkat/L × 60
nkat/L = U/L × 16.667
- U
- 1 unit = 1 µmol of substrate converted per minute
- kat
- 1 katal = 1 mol of substrate converted per second, so 1 U/L = 1/60 µkat/L
- IU/L
- numerically identical to U/L; no conversion is needed between them
- method dependence
- amylase assays differ in substrate and in whether the salivary isoenzyme is inhibited, so reference intervals are not transferable between laboratories
Worked example
Serum amylase 85 U/L
85 ÷ 60 = 1.417 µkat/L
= 1,417 nkat/L = 85 IU/L
Within the adult reference interval of 30–110 U/L
Reference interval in both conventions
| U/L | µkat/L | |
|---|---|---|
| Adult reference interval | 30 – 110 | 0.50 – 1.83 |
| Commonly quoted diagnostic threshold, three times the upper limit | > 330 | > 5.5 |
| Below the interval | < 30 | < 0.50 |
Amylase against lipase in suspected pancreatitis
| Amylase | Lipase | |
|---|---|---|
| Rises after onset | 2 – 12 hours | 4 – 8 hours |
| Returns to normal | 3 – 5 days | 8 – 14 days |
| Useful in late presentation | No | Yes |
| Raised by salivary disease | Yes | No |
| Specificity for the pancreas | Lower | Higher |
Timing, source and why the number is not the severity
Amylase is reported as catalytic activity rather than mass, so the units are U/L or the numerically identical IU/L, and in SI-strict laboratories µkat/L or nkat/L. One unit is one micromole of substrate converted per minute and one katal is one mole per second, which makes the whole conversion a division by 60: an amylase of 85 U/L is 1.417 µkat/L. Nothing about the molecule enters the arithmetic, which is why no molar unit is offered.
The kinetics are the first trap. Amylase rises within a few hours of the onset of acute pancreatitis and falls back into the reference interval within three to five days. A patient who presents on day four with several days of pain can therefore have a completely normal amylase and florid pancreatitis, and a normal result never excludes the diagnosis. Lipase stays raised for one to two weeks and is more specific to the pancreas, which is why most guidelines now prefer it and why measuring both adds little.
The second trap is source. Amylase is not a pancreatic enzyme alone: the salivary glands produce an isoenzyme, so parotitis raises it, and it also rises in bowel perforation and infarction, in ruptured ectopic pregnancy, in diabetic ketoacidosis and in renal impairment, where reduced clearance lifts the level without any acute abdominal pathology. Macroamylasaemia deserves separate mention: amylase bound to immunoglobulin is too large to be filtered, accumulates, and produces a persistently raised amylase with a normal lipase in a well patient. It is benign, and recognising it prevents repeated imaging.
Finally, the degree of elevation does not track severity. A very high amylase is not a severe attack and a modest one is not a mild attack; severity is assessed with the revised Atlanta criteria and with scoring systems built from physiology, organ failure and imaging, none of which uses the enzyme level. Following amylase serially through an admission adds nothing to management.
Frequently asked questions
How do I convert amylase from U/L to µkat/L?
Divide by 60. A unit is one micromole per minute and a katal is one mole per second, so the conversion is purely per-minute to per-second. An amylase of 85 U/L is 1.417 µkat/L, or 1,417 nkat/L.
Does a normal amylase exclude acute pancreatitis?
No. Amylase rises within hours of onset but falls back into the reference interval within three to five days, so a patient presenting late can have a normal result. Lipase stays raised for one to two weeks and is the better test in that situation.
What raises amylase apart from the pancreas?
The salivary glands produce their own isoenzyme, so parotitis raises it. It also rises in bowel perforation and infarction, ruptured ectopic pregnancy, diabetic ketoacidosis and renal impairment, where reduced clearance lifts the level without abdominal pathology.
What is macroamylasaemia?
Amylase bound to immunoglobulin, forming a complex too large to be filtered by the glomerulus. It accumulates and produces a persistently raised amylase with a normal lipase in a well patient. It is benign, and recognising it avoids repeated imaging and admission.
Does a very high amylase mean severe pancreatitis?
No. The height of the rise does not correlate with severity. Severity is graded with the revised Atlanta criteria and with scores built from physiology, organ failure and imaging, none of which includes the enzyme level.
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References
- 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.
- 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.
- IFCC reference procedure for the measurement of catalytic activity concentration of α-amylase at 37°C.