SDMA (Symmetric Dimethylarginine)

What it measures

SDMA is made by the body's cells at a steady rate and removed mainly by the kidneys, so like creatinine it reflects kidney filtration. Unlike creatinine, it does not come from muscle, so it is less likely to be underestimated when a cat loses weight and muscle. A research review describes it as a sensitive early marker of declining kidney function.

What a high value may mean

A persistently high SDMA can mean kidney filtration has dropped. IRIS states that SDMA persistently above 14 µg/dL may be used to diagnose early chronic kidney disease. However, newer studies show that SDMA can also be falsely high: for example, some cats with hyperthyroidism had high SDMA before treatment that returned to normal afterward. A single high result is not necessarily kidney disease, and a recheck together with creatinine and a urine test is usually needed.

What a low value may mean

Studies found that many hyperthyroid cats have low SDMA, because hyperthyroidism speeds up kidney filtration. In these cats the true kidney function may only show after thyroid treatment, so vets usually recheck kidney values after treatment.

Usually read together with

Creatinine, urea nitrogen, and a urine test; in senior cats, thyroxine (T4) is often checked too.

When to follow up

The IRIS SDMA stage cut-offs for cats are: Stage 1 below 18 µg/dL, Stage 2 18–25, Stage 3 26–38, and Stage 4 above 38, again only for cats with confirmed, stable chronic kidney disease. When SDMA and creatinine point to different stages, IRIS has separate guidance, so leave this to your vet. After a single high result, simply arrange a recheck as your vet advises; there is no need to panic.

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