What does SDMA measure in cats?

Symmetric dimethylarginine, usually shortened to SDMA, is a small molecule released during normal protein turnover and cleared mainly by the kidneys. Because it tracks glomerular filtration rate, it can rise when kidney filtration declines. It is not a diagnosis by itself; it is a clue that helps your veterinarian decide whether the kidneys need closer evaluation. Peer-reviewed veterinary studies found SDMA to be closely related to kidney filtration markers and useful alongside creatinine and urinalysis (Hall et al., 2014; Nabity et al., 2015).

For owners, the practical value is context. A cat may look normal while early kidney changes are developing. Creatinine can stay within the reference interval when muscle mass is low or when kidney changes are mild. SDMA gives the veterinarian another angle, especially during senior wellness testing or follow-up after illness. Hyperthyroidism, weight loss, and low muscle mass can complicate interpretation in older cats, so SDMA is useful because it is less dependent on muscle than creatinine.

Why might a veterinarian order SDMA blood testing?

Your veterinarian may order SDMA as part of a wellness panel, a senior screen, a pre-anesthetic workup, or an investigation into drinking, urination, weight loss, vomiting, poor appetite, or dehydration. In cats, kidney disease is staged and managed with a combination of bloodwork, urine concentration, urine protein, blood pressure, imaging when needed, and clinical signs. The International Renal Interest Society recommends a structured staging approach after kidney disease is confirmed (IRIS, 2023).

SDMA is most helpful when it triggers the next right test. A mild increase may lead to a repeat panel, urinalysis, urine culture, blood pressure measurement, and review of medications or diet. A larger or persistent increase may support earlier kidney management. The result should always be interpreted by the veterinarian who knows the cat, hydration status, recent illness, and complete lab picture.

How is SDMA different from creatinine?

Creatinine is a familiar kidney marker, but it is influenced by muscle mass and can remain deceptively low in thin or older animals. SDMA is less tied to muscle, which is why it can be useful when a cat has lost weight or has naturally lower muscle. Studies in veterinary patients have compared SDMA with creatinine and found that SDMA may identify some kidney changes earlier than creatinine alone (Hall et al., 2014; Nabity et al., 2015).

That does not make creatinine obsolete. Creatinine, blood urea nitrogen, phosphorus, electrolytes, urine specific gravity, and urine protein all answer different questions. A single SDMA value is a signpost; the full panel is the map. Veterinarians use trends, repeatability, and other findings to decide whether a result reflects kidney disease, dehydration, lab variation, or another medical issue.

What happens if the SDMA result is high?

A high SDMA result usually leads to confirmation, not panic. Your veterinarian may repeat bloodwork, check a fresh urine sample, measure blood pressure, and look for protein in the urine. They may also review recent medications such as nonsteroidal anti-inflammatory drugs, exposure risks, infection signs, dental disease, and hydration. The Merck Veterinary Manual emphasizes that chronic kidney disease management depends on severity, complications, and ongoing monitoring rather than one isolated number (Merck Veterinary Manual, n.d.).

If kidney disease is confirmed, the plan may include hydration support, nutrition changes, blood pressure treatment, phosphorus control, nausea management, and monitoring intervals. Early detection can be valuable because some complications are easier to manage before the cat feels sick. The goal is not to chase the number; it is to preserve comfort, appetite, hydration, and kidney function for as long as possible.

Can SDMA be falsely increased or confusing?

Yes. Lab values can be affected by hydration, recent illness, sample handling, biologic variation, and conditions outside the kidneys. A mild isolated increase is often rechecked. Veterinarians may look for a pattern: Is the urine dilute? Is creatinine changing? Is blood pressure high? Is there protein in the urine? Are signs present at home? IRIS staging begins after kidney disease is established, so the diagnostic step matters (IRIS, 2023).

Owners should avoid interpreting SDMA as a pass-fail grade. A normal result does not guarantee perfect kidneys, and an abnormal result does not automatically mean advanced kidney failure. It is one measurement in a clinical conversation. The best use is to ask what follow-up is needed and when the value should be trended again.

How should owners prepare for the test?

Most cats need only a routine blood draw, though your clinic may give fasting instructions if other lab tests are being run. Bring a medication and supplement list, note changes in thirst or urination, and mention appetite, weight, vomiting, diarrhea, litter box or house-training changes, and energy. Good history can make the SDMA result far more meaningful.

Ask whether a urine sample should be collected the same day. Bloodwork without urinalysis leaves important questions unanswered, especially urine concentration and protein loss. If the cat is stressed at the clinic, discuss low-stress handling or pre-visit medication. Kidney evaluation is usually a series of calm, practical steps, not a single dramatic event.

What questions should you ask your veterinarian?

Useful questions include: Was the SDMA change mild, moderate, or severe? Should it be repeated? What did the urine show? Is blood pressure normal? Does the cat need imaging, culture, diet change, or medication? How soon should labs be rechecked? These questions turn an unfamiliar biomarker into a care plan.

The most important question is what trend would change management. A stable mildly increased SDMA may be monitored differently from a rising value with dilute urine and weight loss. When you understand the monitoring plan, you can watch the right home signs and avoid both complacency and unnecessary alarm.

References

International Renal Interest Society. (2023). IRIS staging of CKD. Merck Veterinary Manual. (n.d.). Chronic kidney disease in dogs and cats. Nabity, M. B., Lees, G. E., Boggess, M. M., et al. (2015). Symmetric dimethylarginine assay validation, stability, and evaluation as a marker for early detection of chronic kidney disease in dogs. Journal of Veterinary Internal Medicine, 29, 1036–1044. Hall, J. A., Yerramilli, M., Obare, E., et al. (2014). Comparison of serum concentrations of symmetric dimethylarginine and creatinine as kidney function biomarkers in cats. Journal of Veterinary Internal Medicine, 28, 1676–1683. Sparkes, A. H., Caney, S., Chalhoub, S., et al. (2016). ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease. Journal of Feline Medicine and Surgery, 18, 219–239.