Amylase (serum)
Serum amylase levels overlap substantially between pregnant and nonpregnant adults. Elevations must be interpreted with symptoms, lipase, and imaging, since amylase alone is neither specific nor sensitive for pancreatitis—especially in pregnancy.
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| U/L | 20 – 96 | 24 – 83 | 16 – 73 | 15 – 81 |
| µkat/L | 0.33 – 1.6 | 0.40 – 1.38 | 0.27 – 1.22 | 0.25 – 1.35 |
Despite physiologic hemodilution, pregnancy does not significantly lower normal amylase ranges.
Causes of Elevated Amylase (Hyperamylasemia)
- Pregnancy-related
- Acute pancreatitis (gallstones, hypertriglyceridemia, drug-induced)
- Hyperemesis gravidarum (often salivary isoenzyme)
- Cholelithiasis / biliary colic
- Pancreatic causes
- Acute or chronic pancreatitis
- Pancreatic trauma or duct obstruction
- Pancreatic neoplasm
- Non-pancreatic causes
- Salivary gland disease (sialadenitis, bulimia)
- Macroamylasemia
- Renal insufficiency → reduced clearance
- Bowel obstruction, perforation, ischemia
- Ectopic pregnancy (rare amylase elevations)
- DKA and metabolic stress
- Malignancies producing ectopic amylase
- Medications
- Thiazides, azathioprine, valproate, antiretrovirals, others
Lipase is more specific and remains elevated longer than amylase. Normal amylase does not exclude pancreatitis, especially in hypertriglyceridemia.
Causes of Low Amylase (Hypoamylasemia)
- Pancreatic insufficiency
- Advanced chronic pancreatitis
- Cystic fibrosis
- Post-pancreatectomy
- Metabolic conditions
- Marked hypertriglyceridemia (spurious low values)
- Poorly controlled diabetes with pancreatic atrophy
- Advanced liver disease
- Inherited disorders
- Congenital amylase deficiency
- Selective salivary/pancreatic isoamylase deficiency
- Pregnancy note
- Lower-normal values often reflect hemodilution, not pathology.
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.
- Wallach J. Interpretation of Diagnostic Tests. 8th ed.
- Fischbach FT, Dunning MB. Manual of Laboratory and Diagnostic Tests. 7th ed.