By The Pawline veterinary teamVeterinary-reviewed by Alastair Greenway, BVM&S MRCVS · 25 July 2026
Reference range · µg/L
5.745.2
Reference
5.7–45.2
Direction
Lower values are the concern.
This is the conventional reference interval. Your pet’s own report may print a slightly different range — always read the value against that. Sign in to see your pet’s value on this strip.
TLI checks whether the pancreas is producing enough digestive enzymes. A low value is the defining test for exocrine pancreatic insufficiency (EPI) — a treatable cause of weight loss despite a big appetite — so it turns a frustrating, mysterious problem into a manageable one.
TLI (trypsin-like immunoreactivity) measures the blood level of a pancreatic digestive enzyme precursor. The pancreas has two jobs: making insulin (its endocrine role) and making the enzymes that digest food (its exocrine role). TLI reports on the exocrine side — specifically, whether the pancreas is producing enough digestive enzyme. It is the gold-standard test for one specific, very treatable condition.
TLI reflects the pancreas's output of digestive enzymes. A low value is the defining test for exocrine pancreatic insufficiency (EPI).
Reading a low result
A low TLI is the diagnostic finding for exocrine pancreatic insufficiency (EPI) — the pancreas no longer makes enough digestive enzyme, so food passes through undigested. The classic picture is a young-to-middle-aged dog (German Shepherds are over-represented) that is losing weight despite a ravenous appetite, often with loose, pale, greasy, voluminous stools. EPI can look mysterious and severe, yet a low TLI both explains it and points straight to the treatment: replacing the missing enzymes with every meal. Few lab results turn a distressing problem into a manageable one so directly.
Because EPI also impairs B12 absorption, a low TLI is usually accompanied by a check of B12 (and often folate), and B12 is supplemented alongside enzyme replacement.
Reading a high or normal result
A normal TLI effectively rules out EPI, which is its main purpose. A high TLI can occur transiently with pancreatitis (a leaking, inflamed pancreas releasing enzyme into the blood), though pancreatitis is better assessed with pancreatic lipase; a high TLI can also rise with reduced kidney clearance. In the context of investigating weight loss and diarrhoea, it is the low end that carries the key message.
In chronic disease
EPI is a lifelong condition, and once diagnosed by a low TLI, management is monitored clinically — weight, appetite and stool quality — rather than by repeating TLI, since the pancreatic deficit is permanent. B12 status, however, is tracked and supplemented over time. So TLI is mostly a diagnostic test rather than a monitoring one, but it is the number that unlocks the whole management plan.
Cat vs dog
TLI is species-specific — the assay differs for dogs (cTLI) and cats (fTLI) — and EPI, while classically canine, does occur in cats too, where it is often linked to chronic pancreatitis and is under-recognised. In both species, a low TLI in a weight-losing, hungry patient with poor stools is the finding that makes the diagnosis. The reference ranges differ between the species and the correct assay must be used.
How it's measured
TLI is measured from a fasted blood sample (a recent meal can affect it) at a laboratory running the gastrointestinal panel, using the species-appropriate assay, reported in µg/L. It is usually run with B12 and folate. Read the value against your own report's range.
What to do next
In a pet losing weight despite a good or increased appetite, especially with greasy, bulky stools, a low TLI confirms EPI and points to lifelong enzyme replacement plus B12 support — a highly effective treatment. If TLI is normal, the weight loss and diarrhoea are pursued down other avenues with your vet. Either way, TLI is one of the most decisive tests in the gastrointestinal work-up.
Reference ranges reflect conventional laboratory intervals. Always interpret against your own lab's printed range and your veterinary surgeon's judgement. A brighter optimal band is shown only where a published guideline defines one, and it is cited.
This page is educational and is not a diagnosis. Lab results are interpreted in the full clinical context by your veterinary surgeon; a single value rarely tells the whole story.
