Vitamin B12 is essential for red blood cell formation, nervous system function, and DNA synthesis. It is unique among vitamins in that it is found almost exclusively in animal-based foods — dogs on heavily plant-based diets are at risk of deficiency. B12 also works closely with folate (B9) in cell division, and a deficiency in either vitamin can mimic the other.
A single sardine provides roughly 8–10mcg of vitamin B12 — a medium dog needs approximately 8.75–25mcg per day. Sardines, salmon, beef, tuna, and eggs are excellent sources. Dogs with chronic digestive conditions may need B12 injections from their vet, as oral supplementation is ineffective when absorption is impaired.
0.0% of daily nutrient intake
Vitamin B12 (Cobalamin) makes up 0.0% of your dog's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Lethargy, weight loss, poor appetite, chronic diarrhea, anemia (large, immature red blood cells), and neurological symptoms in severe cases. Some breeds and dogs with gastrointestinal conditions (exocrine pancreatic insufficiency, inflammatory bowel disease) are prone to B12 malabsorption regardless of dietary intake.
B12 is water-soluble with an extremely wide safety margin. Excess is excreted in urine and toxicity from dietary or supplemental sources is not a concern.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | medium 10-25kg | 8.75 | 25 | mcg | NRC recommended allowance. B12 is found only in animal-source foods. Dogs with GI disease may malabsorb B12. |
| Senior | medium 10-25kg | 8.75 | 25 | mcg | Senior dogs maintain similar B12 needs. Monitor for deficiency signs if your dog has chronic digestive issues. |
Source: NRC 2006
Folate and B12 work together in the methylation cycle, which is essential for DNA synthesis and red blood cell maturation. Deficiency in either vitamin causes megaloblastic anemia with large, immature red blood cells.
What this means: When evaluating anemia or poor blood work, check both folate and B12 levels. Supplementing one without the other may mask the deficiency of the missing vitamin. Eggs and salmon provide both nutrients naturally, supporting the methylation cycle from both sides.
