Cobalamin (vitamin B12) in cats and dogs

What it shows

B12 is absorbed in the ileum, the last part of the small intestine, and its absorption depends on the exocrine pancreas — the part of the pancreas that makes digestive enzymes. So the blood level reflects two things at once: how healthy the end of the small intestine is and whether the pancreas works well enough. Gut bacteria also use cobalamin, so too many bacteria in the small intestine (dysbiosis) can lower it as well.

A deficiency caused by diet is very unlikely: even several weeks of starvation do not push a dog’s level below the range. On the other hand, not every gut disease lowers B12 — a mild or short illness may not use up the body’s stores, so a result inside the range does not rule out intestinal disease.

Higher than reference — what it may be a sign of

• Recent vitamin B12 from the vet or a supplement — it raises the result, so the vet needs to know about it before reading the form.
• Without any B12 given — the Texas A&M Gastrointestinal Laboratory states that values above the reference interval have no proven significance.

Lower than reference

A low cobalamin is the finding that matters. It may be a sign of:

• Disease of the distal small intestine — chronic enteropathies; low B12 is particularly associated with inflammatory bowel disease (IBD) and intestinal lymphoma.
• Exocrine pancreatic insufficiency (EPI) — more than 80% of dogs and almost all cats with EPI are cobalamin deficient.
• Small intestinal dysbiosis — bacteria use up the vitamin before the gut can absorb it; this can come together with a high folate.

Because absorption depends on the pancreas, a low B12 in a dog or cat is a reason for the vet to check pancreatic function with TLI, if it has not been done yet.

Look at together with

• Folate — absorbed at the other end of the small intestine, so the pair helps to tell where the problem is. Both low — disease spread along the small intestine; low B12 with high folate — possible dysbiosis.
• TLI — the main test for exocrine pancreatic insufficiency; B12 and folate are routinely measured alongside it.
• Pancreatic lipase (cPL, fPL) — answers a different question: inflammation of the pancreas, not a lack of enzymes.
• Albumin — in cats with chronic gut disease, a very low cobalamin together with a low albumin is associated with a poorer outlook.
• Ammonia — cobalamin deficiency has been linked to high ammonia in dogs and cats.

Units and conversion

Labs report cobalamin in ng/L or pg/mL — the same number, because 1 pg/mL equals 1 ng/L — and some in pmol/L. 1 pmol/L is about 1.355 ng/L, so 300 pmol/L is about 407 ng/L, and 300 ng/L is about 221 pmol/L. In the app each row keeps the unit printed on the form; the chart converts to one unit so forms from different labs line up.

Reference range

The reference range is on your lab’s form. Labs set their own intervals, and the intervals for dogs and cats are different, so a value is read against the interval printed next to it. A fasted sample, 8–12 hours without food, is recommended. B12 and folate are sensitive to light, so the tube should not stand in direct sunlight, and some laboratories do not accept EDTA plasma for this test — the clinic will use a plain serum tube. A value slightly below the interval is read by the vet together with signs, folate and TLI rather than on its own.

Cats and dogs

Sources

1. Texas A&M Gastrointestinal Laboratory — Serum Cobalamin (Vitamin B12) and Folate (Vitamin B9)
2. Texas A&M Gastrointestinal Laboratory — Frequently Asked Questions
3. Malabsorption Syndromes in Small Animals. Merck Veterinary Manual
4. Exocrine Pancreatic Insufficiency in Dogs and Cats. Merck Veterinary Manual
5. Cornell University Animal Health Diagnostic Center — Canine, Feline and Equine Metabolic Function Tests
6. IDEXX — Clinical Approach to Chronic GI Disease in the Feline Patient
7. eClinPath (Cornell University College of Veterinary Medicine) — Ammonia