LFT vs KFT: Liver and Kidney Function Tests for Pets Explained

A liver function test (LFT) checks how well the liver is working, and a kidney function test (KFT) checks how well the kidneys clear waste from the blood. Both use a small blood sample, and your registered veterinarian reads them together with your pet's signs and history.

LFT and KFT at a glance

• LFT (liver): usually includes the liver enzymes ALT (SGPT), AST (SGOT) and ALP, plus bilirubin and proteins such as albumin. It can help detect liver cell damage, bile flow problems and jaundice.
• KFT (kidney): usually includes urea (some labs report it as BUN) and creatinine, and sometimes minerals such as phosphorus and potassium. It can help detect reduced kidney function.
• Sample: both use serum, which is the clear fluid left when blood has clotted. The lab needs about 2 mL for each test.
• Limits: neither test gives a diagnosis on its own. The exact list of items can differ between labs, so check your report.

What an LFT shows

The liver cleans the blood, makes proteins, helps digest fat and stores energy. The Liver Function Test (LFT) looks at several liver markers:

• ALT (SGPT): an enzyme inside liver cells. Enzymes are proteins that do work in the body. ALT leaks into the blood when liver cells are damaged.
• AST (SGOT): found in the liver and in muscle, so muscle injury can raise it too.
• ALP: linked to the bile ducts (the small tubes that carry bile out of the liver) and to bone. It can be higher in growing puppies and with some medicines.
• Bilirubin: a yellow pigment. A high level may cause jaundice, which is a yellow colour in the gums, eyes or skin.
• Albumin: a protein made by the liver. A low level may be seen in some liver diseases, and also when protein is lost through the kidneys or gut.

The name "function test" can mislead. Most liver enzymes show damage, not how well the liver works. If your vet suspects poor liver function, tests such as Ammonia, a waste product that can build up when the liver is not clearing it, may be added.

What a KFT shows

The kidneys filter waste out of the blood and make urine. The Kidney Function Test (KFT) measures two waste products:

• Creatinine: a waste product from muscles. It rises in the blood when the kidneys are not filtering well.
• Urea: a waste product from protein. It also rises when kidney filtering falls.

Dehydration, a high-protein meal or bleeding in the gut can also raise urea, and dehydration can raise creatinine too. So vets often check the urine as well, to see how well the kidneys are concentrating it.

Creatinine and urea usually rise only after the kidneys have already lost a good part of their working ability. A newer test, SDMA (Symmetric Dimethylarginine), may rise earlier in some pets and can help detect early kidney problems.

Why vets often ask for both

Liver and kidney problems can look alike from the outside. Both can cause poor appetite, vomiting, tiredness and weight loss. Some signs give extra clues:

• Liver: yellow gums, eyes or skin, or a swollen belly.
• Kidney: drinking and urinating much more, bad breath and mouth sores.

Drinking and urinating more can also be caused by diabetes, a womb infection in an unspayed female and other illnesses. Only tests can sort out the reason. Vets also ask for both tests because:

• Both organs help the body handle anaesthetic drugs, so both are checked before surgery.
• Some long-term medicines are monitored with an LFT and KFT from time to time.
• Older pets get regular check-ups, because liver and kidney disease become more common with age.
• Serious infections, including tick fever, can affect both organs.

The Comprehensive Vital Panel puts a CBC, KFT, LFT, blood parasite smear and blood sugar into one visit.

Reading your report

Each result is printed beside a reference range. A value outside the range is a clue, not a diagnosis. A small rise can be temporary, for example after some medicines or a muscle injury. A big change, or a value that keeps rising on repeat tests, matters more.

Ranges differ between dogs, cats and labs, so use the range on your own report. Keep old reports, so your vet can follow the trend. Blood is taken from a vein, left to clot, and the clear serum is separated for testing. Routine tests are normally reported the same day or within 24 hours.

When to talk to your vet

Show the report to your vet even if only one value is high or low. A single result may be temporary, so your vet may repeat the test or add others, such as a urine test. Do not give any tonic, supplement or human medicine because of a report.

See a vet urgently if your pet:

• has yellow gums or eyes
• vomits again and again
• passes very little or no urine
• has a swollen belly, has fits or collapses

Pashupatinath Vet Lab provides free sample collection anywhere in Bhopal. Call or WhatsApp +91 88175 01118 to book. From other towns, samples can be sent to the lab by courier, bus parcel or through your local veterinarian, and the lab coordinates with you by phone or WhatsApp.