A five year old male castrated mixed breed dog was presented to Cornell University Hospital for Animals Medicine Service with a one month history of progressive tetraparesis and anemia. On presentation, the physical examination abnormalities included generalized muscle wasting and paresis that were more pronounced in the hindlimbs resulting in the dog ambulating in a frog-like posture. Neurologic examination demonstrated deficits in proprioceptive placing and hopping in both hindlimbs with reduced reflexes in all limbs. A complete blood count showed a severely microcytic, hypochromic mild anemia with siderocytes and fragmented red blood cells consistent with a functional iron deficiency. Lead levels, acetylcholine receptor antibody titers, and infectious disease titers were all negative. A gastrointestinal panel showed undetectable vitamin B12 (cobalamin) and low vitamin B9 (folate) concentrations. Vitamin B6 (pyridoxine) concentrations were measured at a laboratory performing testing on human samples and were found to be 40-fold lower than a healthy canine control. The dog was diagnosed with a presumptive functional iron deficiency secondary to vitamin B6 deficiency and prescribed a treatment trial of twice weekly subcutaneous vitamin B complex injections. Recheck examination two months later showed near normal neuromuscular function and markedly improved hematologic test results, with a resolution of the anemia, an increasing mean cell volume, decreased proportions of microcytic, hypochromic red blood cells, and reduced red blood cell fragmentation with no siderocytes on blood smear evaluation.