Alkaline phosphatase (ALP)
Chemistry ·Also called: ALP, ALKP, AP, SAP, alk phos, alkaline phosphatase
What it is
ALP comes from several sources. The liver form rises when bile flow is impeded. The bone form rises in growing animals and in bone disease. Dogs also have a third, steroid-induced form that no other species produces in the same way.
Why your vet measures it
In dogs, a raised ALP alone is common and often benign, especially in older animals, growing puppies, or dogs on steroids. In cats, the picture is the opposite: feline ALP is present in small amounts and clears quickly, so any clear rise in a cat is taken seriously.
What a high result can mean
- Reduced bile flow — gallbladder disease, a stone, pancreatitis pressing on the bile duct, or a mass
- Steroid treatment, or Cushing's disease, in dogs
- Normal bone growth in puppies and kittens, or healing after a fracture
- Long-term phenobarbital treatment in dogs
- Benign nodular changes in the liver of older dogs
- In cats, hepatic lipidosis, cholangitis, or hyperthyroidism
What a low result can mean
- Not clinically significant
Dogs and cats differ
This is the enzyme where dogs and cats diverge most. A mildly raised ALP in an otherwise well older dog is often watched rather than chased. The same relative rise in a cat warrants investigation, because cats simply do not raise ALP without a reason — hepatic lipidosis in a cat that has stopped eating is the classic cause.
Questions worth asking your vet
- Is my dog on any steroid — including ear drops, skin creams and eye preparations?
- Is the GGT raised as well, and what does the combination suggest?
- For a cat: has there been any period of not eating recently?
- Does this need an ultrasound, or a recheck first?
Related terms
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