SDMA in Cats: What the Kidney Test Means
SDMA is an early kidney marker in cats that rises before creatinine. Learn the normal range (14 ug/dL or less), what a high SDMA means, and why it matters.
Quick definition: SDMA (symmetric dimethylarginine) is a blood test that estimates kidney filtration in cats. A normal SDMA is 14 ug/dL or less. It rises once about 25 to 40 percent of kidney function is lost, often years before creatinine becomes abnormal, which makes it one of the earliest markers of feline chronic kidney disease.
If your senior cat's bloodwork lists SDMA, it is one of the most useful early-warning numbers on the page. SDMA is a byproduct your body makes constantly and the kidneys clear. When filtration drops, SDMA builds up in the blood, so a rising value signals the kidneys are slowing down.
What makes SDMA special is timing. Older markers like creatinine only cross into the abnormal range after most kidney function is already gone. SDMA flags trouble much earlier, which gives you and your veterinarian a head start on protecting your cat's kidneys.
What SDMA Measures
SDMA reflects the glomerular filtration rate, which is how efficiently the kidneys filter waste from the blood. Because the body produces SDMA at a steady rate and the kidneys are responsible for clearing it, the blood level rises predictably as filtration falls. Unlike creatinine, SDMA is not influenced by muscle mass, so it stays accurate even in thin, muscle-wasted senior cats.
Normal SDMA Range and What the Numbers Mean
| SDMA Value | General Interpretation |
|---|---|
| 0 to 14 ug/dL | Normal kidney filtration |
| 15 to 17 ug/dL | Borderline; recheck to confirm a trend |
| 18 to 25 ug/dL | Mild to moderate loss of kidney function |
| Above 25 ug/dL | More significant loss; often higher IRIS stages |
These are general guideposts. Reference ranges vary by laboratory, and a single value is never a diagnosis on its own. Your veterinarian looks at SDMA together with creatinine and BUN, urine specific gravity, phosphorus, and blood pressure, then watches the trend across visits.
Why SDMA Matters in Senior Cats
Chronic kidney disease is one of the most common conditions in cats over 10. Catching it early, while the cat still feels well, lets you act before symptoms like increased thirst, weight loss, or poor appetite appear. Early steps can include a therapeutic renal diet, careful phosphorus control, treating high blood pressure, and keeping the cat well hydrated. SDMA is the number that often makes that early action possible.
A high SDMA does not automatically mean advanced disease. It is the start of a conversation. Your vet will usually confirm the value is persistent, rule out dehydration, and stage the disease using International Renal Interest Society (IRIS) criteria.
SDMA and IRIS Staging
The IRIS system stages chronic kidney disease mainly using creatinine, with SDMA as a supporting marker. A persistently elevated SDMA in a cat with normal creatinine can support a diagnosis of early disease, and SDMA can help confirm staging in thin cats whose creatinine may read falsely low. To see how the stages line up, review the IRIS CKD staging chart for cats and the broader senior cat normal lab values.
What to Do If Your Cat's SDMA Is High
- Ask your vet whether a recheck in two to four weeks is appropriate to confirm a true trend.
- Make sure your cat is well hydrated, since dehydration can raise SDMA temporarily.
- Request the full panel and a urine test, including urine specific gravity and a urine protein check.
- Keep copies of every report so you can track the number over time.
- Learn the bigger picture in our guide to kidney disease in senior cats.
This page is educational and complements, but does not replace, your veterinarian. Always discuss your cat's specific results with a professional who knows their history.
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Frequently Asked Questions
What is a normal SDMA level for a cat?
A normal SDMA (symmetric dimethylarginine) is 14 ug/dL or less. Many laboratories flag values of 15 to 17 ug/dL as borderline and worth rechecking, while results above 18 ug/dL more strongly suggest reduced kidney function. As with all lab values, your veterinarian interprets SDMA alongside creatinine, urine concentration, and your cat trends over time.
Why does SDMA rise before creatinine?
SDMA is a kidney filtration marker that climbs once roughly 25 to 40 percent of kidney function is lost, while creatinine often stays normal until about 75 percent is gone. SDMA is also less affected by muscle mass, so it stays reliable in thin senior cats whose low muscle can falsely lower creatinine. That early signal lets vets catch chronic kidney disease sooner.
My cat has a high SDMA but normal creatinine. What does that mean?
This pattern often points to early kidney disease, IRIS Stage 1 or early Stage 2, where filtration is starting to decline but creatinine has not yet crossed its reference range. Your vet will usually recheck SDMA in a few weeks to confirm it is persistent, check urine specific gravity, and look for other causes. A persistently elevated SDMA is rarely ignored in an older cat.
Can SDMA be high for reasons other than kidney disease?
Yes, though kidney disease is the most common reason in senior cats. Dehydration and any condition that reduces blood flow to the kidneys can raise SDMA temporarily. A single high value is not a diagnosis, which is why vets confirm it is repeatable, rehydrate the cat if needed, and review the full panel and urine test before concluding chronic kidney disease.
How often should a senior cat have an SDMA test?
Most vets include SDMA in routine senior bloodwork at least once a year from about age 7, and twice a year from 11 onward or sooner if a cat has kidney disease. If an SDMA is borderline, a recheck in two to four weeks helps confirm whether it is a true trend. Building a baseline makes small upward shifts easy to spot.
Does a high SDMA mean my cat needs a kidney diet right away?
Not automatically. A single borderline SDMA with otherwise normal results usually prompts a recheck rather than an immediate diet change. Once your vet confirms chronic kidney disease and stages it using IRIS criteria, a therapeutic renal diet and other steps may be recommended. Diet and treatment decisions belong with your veterinarian, who knows your cat full history.
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