Vitamins A, E and B1 in cats and dogs
Vitamins A, E and B1 (thiamine) are special tests, not routine bloodwork. A vet orders them when signs and the diet history point to a particular shortage or excess. The number supports the picture but does not settle it alone: a thiamine shortage, for example, is diagnosed by the signs, the diet and how the animal responds when the vet gives thiamine.
What it shows
A vet orders these vitamins from a specialised laboratory when signs and diet history point to a shortage or excess.
- Vitamin A (retinol) — a fat-soluble vitamin. Cats need it in ready-made (preformed) form from food; in excess it damages bone.
- Vitamin E (alpha-tocopherol) — works as an antioxidant in the body.
- Vitamin B1 (thiamine) — needed by the nervous system; an acute shortage gives severe neurological signs.
Vitamins A and E are measured in serum. The serum is separated from the clot, kept out of direct sunlight, chilled and shipped on ice, and haemolysis is avoided. Thiamine is measured in whole blood, directly by chromatography (HPLC) or indirectly through an enzyme in red cells (erythrocyte transketolase activity); the indirect tests can be affected by many factors. Few laboratories do thiamine routinely, and routine bloodwork reflects a thiamine shortage poorly.
Higher than reference — what it may be a sign of
- Vitamin A — chronic excess (hypervitaminosis A) in cats and dogs fed diets made largely of liver. It causes bony outgrowths, most prominent along the neck and upper back; they are seen on X-rays, and serum vitamin A can be measured to support the diagnosis. In dogs the signs of excess include skeletal malformation, spontaneous fractures and internal bleeding.
- Vitamin E and thiamine — the sources used here do not describe a clinical meaning of a high value; the vet reads it together with the lab.
Lower than reference
- Thiamine — a shortage is described after diets made mostly of raw freshwater fish or clams (they contain an enzyme that destroys thiamine), meat preserved with sulphites (sulphur dioxide), and some commercial cat foods recalled for low thiamine (six recalls in North America since 2010, as of 2017). Diuretics may add to the risk. The diagnosis rests on signs, diet history and whether the signs reverse after the vet gives thiamine; a blood value supports it.
- Vitamin E — a shortage has occurred in cats given large amounts of canned tuna, causing inflammation of body fat (pansteatitis, “yellow fat disease”) and inflammation in muscles and the heart.
- Vitamin A — a shortage can be seen in serum; in farm animals a liver sample is described as most sensitive.
Look at together with
- Diet history — what and since when the animal eats; the vet reads the result next to it.
- X-rays of the spine — when vitamin A excess is suspected.
- Neurological examination — when a thiamine shortage is suspected.
- Taurine — another nutrient a vet may check when illness may be linked to the diet.
- Other vitamins on the form: vitamin D, cobalamin (B12), folate.
Units and conversion
Vitamin A is reported in µmol/L or µg/dL: 1 µg/dL equals 0.03491 µmol/L, so 100 µg/dL is about 3.49 µmol/L. Vitamin E is reported in µmol/L or µg/mL: 1 µg/mL equals 2.322 µmol/L, so 10 µg/mL is about 23.2 µmol/L. Thiamine is reported in nmol/L. An indirect thiamine test (enzyme activity in red cells) is a different kind of result and cannot be put on one line with whole-blood thiamine. 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. For these vitamins ranges come from the laboratory that ran the test, and for thiamine little is known about normal blood levels in dogs and cats, so the interval of one lab may not match another. A value is read against the interval printed next to it and always together with the signs and diet history. Thiamine in whole blood is stable for up to 48 hours at room temperature; the lab gives its own shipping rules.
Cats and dogs
Cats need vitamin A in preformed form and are more sensitive to excess than dogs: growing kittens fed a diet high in liver can develop bone overgrowth of the first neck vertebrae. Thiamine shortage is described in both cats and dogs; in cats signs include poor appetite, seizures, muscle weakness and a downward bending of the neck (cervical ventroflexion). Vitamin E shortage in cats has been linked to large amounts of canned tuna.
Dogs are less sensitive to excess vitamin A than cats. Signs of thiamine shortage in dogs include unsteady gait (ataxia) and an enlarged heart muscle (cardiac hypertrophy).
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
- Sanderson SL. Nutritional Requirements of Small Animals. Merck Veterinary Manual, professional version, full review November 2023.
- Thomas WB. Nutritional Disorders of the Spinal Column and Cord in Animals. Merck Veterinary Manual, professional version, full review October 2026.
- Kritikos G, Parr JM, Verbrugghe A. The Role of Thiamine and Effects of Deficiency in Dogs and Cats. Veterinary Sciences, 2017; 4(4):59.
- Michigan State University Veterinary Diagnostic Laboratory. Vitamin A and E Diagnostics.
- Michigan State University Veterinary Diagnostic Laboratory. Mineral and Vitamin Testing — Sample Collection and Handling.
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.