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A high SDMA in cats alongside a normal creatinine means the kidneys have lost some filtering capacity, but not enough for creatinine to show it yet. That is the earliest a routine blood panel can pick this up, which is why most cats with this result are still eating, drinking and behaving normally when it turns up.
SDMA is released into the blood as cells break down and rebuild proteins, and the kidneys clear almost all of it, which is why its level tracks filtration closely. Blood creatinine usually does not rise until a cat has lost almost 75 percent of kidney function, while SDMA can be detected at about 40 percent loss [Cornell Feline Health Center]. In one group of cats, SDMA rose above the normal limit a mean of 17 months before creatinine did. The range ran from 1.5 to 48 months [Today’s Veterinary Practice].
What Does SDMA on the Bloodwork Measure?
Symmetric dimethylarginine, or SDMA, is a small molecule that cells throughout the body release at a steady rate as they turn over. The kidneys are the main way it leaves the blood.
Because filtration is what clears it, a rising SDMA points fairly directly at filtration that has slipped. Creatinine measures the same thing by a different route, but it has a blind spot that SDMA does not, and the blind spot is worst in older, thinner cats.
SDMA is cleared almost entirely by the kidneys, making it a sensitive marker of filtration. Unlike creatinine, SDMA is not significantly affected by muscle mass.
Why Is SDMA Useful in Cats Specifically?
Creatinine is partly a byproduct of muscle, so a thin, muscle-wasted senior cat can post a comfortable-looking creatinine while real kidney disease is present. Those are also the cats in whom kidney disease is most likely. SDMA should not be affected by changes in muscle mass [Today’s Veterinary Practice], so it still means something in a cat who has been losing condition.
SDMA does not share that blind spot, which is why it can flag reduced kidney function earlier than creatinine, sometimes catching a meaningful decline in filtration well before creatinine rises out of range. This is especially valuable in cats, since chronic kidney disease is so common in the senior population and early detection genuinely changes how proactively we can manage it.
SDMA now sits inside the international staging system for feline kidney disease. IRIS stages cats on fasting creatinine, fasting SDMA, or preferably both. A persistently raised SDMA above 14 ug/dL can be used to diagnose early chronic kidney disease [IRIS staging guidelines, 2026].
Why Does SDMA Rise in Cats?
SDMA rises for largely the same reasons creatinine does, since both reflect kidney filtration, though SDMA tends to move first.
Chronic kidney disease is the most common reason for a persistently elevated SDMA in senior cats, often appearing before creatinine or clinical signs do. Acute kidney injury, dehydration, and, less commonly, certain non-kidney illnesses can also raise SDMA, though it is generally considered less influenced by outside factors than BUN.
Not every high SDMA is kidney disease. At the usual cut-off it is about as sensitive as creatinine in cats but less specific, roughly 71 percent against 94 to 96 percent [eClinPath, Cornell], which in practice means one mildly raised SDMA throws more false alarms than a raised creatinine does. Add ordinary lab variation and you have the reason a mild rise gets confirmed on a second sample before anyone acts on it.
Thyroid disease complicates this. An overactive thyroid raises filtration, and many hyperthyroid cats have a low SDMA, under 10 ug/dL, which can hide kidney disease sitting underneath [eClinPath, Cornell]. Among 262 hyperthyroid cats treated with radioiodine, 16 percent had kidney values in the abnormal range when rechecked at a median of 6 months, and SDMA taken before treatment caught only a third of them, with sensitivity 33 percent and specificity 98 percent [Peterson et al, JVIM 2018]. In a hyperthyroid cat, then, a high SDMA is worth acting on, but a normal one is not enough to say the kidneys are fine.
What Does a Mildly High SDMA Usually Mean?
A mildly high SDMA with a completely normal creatinine in a senior cat is a common and useful early finding. It does not mean advanced disease. It means we have a head start.
Cats usually show no signs until stage III or IV, when the kidneys are down to less than 25 percent of usual capacity [Merck Veterinary Manual]. So a cat who looks perfectly well is not evidence against the result.
The usual next step is to repeat SDMA and creatinine in about two to four weeks, alongside a urine test. That is the interval IRIS uses to confirm a value and rule out quiet dehydration [IRIS]. If things look stable, rechecking roughly every three months follows the trend, and repeated values tell you far more than any single result [Today’s Veterinary Practice].
A single mildly elevated SDMA, especially with normal creatinine, is an early signal worth monitoring, not an urgent problem.
If the SDMA stays high on recheck, that confirms early kidney changes worth actively managing.
When Is High SDMA Something to Worry About?
SDMA deserves closer attention when it is markedly high, rises together with creatinine or BUN, or comes with symptoms. The signs to watch for at home include:
- Increased thirst and urination
- Weight loss despite normal eating
- Decreased appetite or vomiting
- Sores in the mouth or a change in breath
- A dull or unkempt coat
If you notice these signs alongside a high SDMA, contact your veterinarian to discuss further evaluation and staging.
A cat who has stopped eating entirely, is profoundly lethargic, or collapses alongside a high SDMA needs prompt veterinary care, since this combination can reflect more advanced disease that needs immediate attention.
How Do Veterinarians Interpret High SDMA?
Vets read SDMA alongside creatinine, BUN, urine concentration, and your cat’s body condition. When SDMA is high but creatinine and urine concentration are still normal, that is the early picture the test was designed to find.
Confirming a lasting rise, then placing it into IRIS staging, is the standard next step. Staging is meant for a well hydrated, stable cat, and it uses blood measured on at least two occasions. It is not applied to one sample drawn on a sick day [IRIS staging guidelines, 2026]. If creatinine is still normal, below 1.6 mg/dL, but SDMA stays above 18 ug/dL, IRIS directs the vet to stage and treat that cat as Stage 2 [IRIS staging guidelines, 2026].
| Pattern | What it often suggests |
|---|---|
| Mildly high SDMA, normal creatinine, thin senior cat | Early kidney change; monitor and recheck |
| High SDMA confirmed on recheck | Early chronic kidney disease; staging begins |
| High SDMA with elevated creatinine and BUN | More established kidney disease |
| High SDMA with severe symptoms | More advanced disease; prompt evaluation |
Trends over repeated checks, not a single value, are what confirm a true early kidney change.
What Happens Next After a High SDMA Result?
For a mild, unconfirmed rise, a recheck alongside creatinine and a urine test is often the sensible first step. Once it is confirmed, your vet will usually start staging and talk about monitoring, and possibly diet, earlier in the disease than creatinine alone would have allowed.
Routine senior bloodwork that includes SDMA, even in cats who seem healthy, remains one of the most useful things you can do.
For a veterinary overview of feline kidney disease, its signs, and long-term monitoring, see the Merck Veterinary Manual guide to noninfectious urinary disorders in cats.
Further Reading
Cat Blood Test Results Explained is the pillar guide to the whole panel, useful for seeing how SDMA fits alongside the other kidney values.
High Creatinine in Cats covers the companion marker that SDMA is designed to complement, especially in cats with reduced muscle mass.
Stages of Kidney Disease in Cats explains how SDMA is incorporated into the IRIS staging system referenced here.
Signs of Kidney Failure in Cats is a useful companion for connecting these early lab findings to what you might notice at home.
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