VetVaultSDMA blood test in cats: what a high SDMA means
SDMA is a blood marker of how well a cat's kidneys filter. On the IDEXX test that IRIS guidance is based on, the usual upper limit is 14 µg/dL. A single mildly high result (15–17) is a reason to recheck, not a diagnosis: vets repeat it in a hydrated cat, with creatinine and a urine test.
What SDMA is and what it measures
Symmetric dimethylarginine is a slightly modified form of the amino acid arginine. Cells throughout the body release it at a fairly steady rate as they break down and recycle their proteins, and the kidneys clear it from the blood. Because production is steady, the blood level depends mainly on the GFR: how much blood the kidneys filter each minute. When GFR falls, SDMA builds up.
That is the same logic as creatinine, the traditional kidney value. The difference is the source. Creatinine is a waste product of muscle, so it depends partly on how much muscle a cat carries; SDMA does not. The ISFM consensus guidelines describe SDMA as a surrogate marker of GFR that does not appear to be affected by muscle mass, which is why it is especially useful in thin senior cats.
SDMA is usually reported in micrograms per decilitre (µg/dL). If your report uses another unit, compare the result only with the range printed beside it.
Normal SDMA in cats, and what 15 or higher means
On the IDEXX method, the usual upper limit for cats is 14 µg/dL. eClinPath, Cornell's clinical pathology reference, gives the same recommended limit and notes that newer studies suggest a higher cut-off may separate healthy and affected animals better. Other laboratories may use different methods and limits, so the range printed on your cat's report comes first. The bands below are approximate and based on the IDEXX method.
| SDMA (µg/dL) | Where it sits | What it can mean |
|---|---|---|
| 14 or lower | Within the usual range | No sign of reduced filtration from SDMA; creatinine and urine results still matter, because no single marker catches every case |
| 15–17 | Mildly above the usual limit | Early reduced filtration, dehydration on the day, or ordinary test variation; a recheck is the usual next step |
| 18–25 | IRIS stage 2 SDMA band | Reduced filtration is more likely if the value persists in a hydrated cat |
| 26 or higher | IRIS stage 3 band (above 38: stage 4 band) | Moderately to markedly reduced filtration if persistent |
The IRIS bands only apply to a stable, hydrated cat that has already been diagnosed with CKD. The 2026 IRIS recommendations state plainly that an increased creatinine or SDMA alone is not diagnostic of CKD. For the full staging table with creatinine, urine protein and blood pressure, see our guide to cat kidney values and IRIS stages.
When to call the vet urgently
Contact your vet or an emergency clinic straight away, whatever the SDMA result, if your cat:
- has not eaten for more than 24 hours;
- is vomiting repeatedly;
- is straining in the litter box or passing little or no urine (a urinary blockage is an emergency, especially in male cats);
- is suddenly weak, wobbly, collapsing or hiding.
Also call promptly if a new test shows very high kidney values, even if your cat seems well.
SDMA vs creatinine in cats
Vets rarely choose one over the other. They measure both because each covers a weakness of the other.
| Feature | SDMA | Creatinine |
|---|---|---|
| Where it comes from | Protein turnover in cells throughout the body | Muscle |
| Effect of muscle mass | Little or none | Low muscle lowers it; well-muscled cats run higher |
| When it rises (Cornell Feline Health Center) | Detectable at about 40% loss of kidney function | Generally not until almost 75% is lost |
| Standardized between laboratories | No; IRIS cut-offs are based on the IDEXX method | Widely measured, but ranges still differ between laboratories |
| Role in IRIS staging | Used alongside creatinine; a persistently higher SDMA can move a cat up a stage | The long-established staging value, ideally fasting and on at least two occasions |
Earlier on average is not the same as always better. eClinPath summarizes newer studies in which SDMA was not a clearly better marker of filtration than creatinine. In one feline study, SDMA at the 14 cut-off was about as good as creatinine at picking up reduced filtration but flagged more cats whose filtration was actually normal; a higher cut-off cut the false alarms at the cost of missing some cases. That trade-off is why a single mildly high SDMA calls for a recheck, and why vets also look at urine specific gravity.
When SDMA can mislead
- Methods are not standardized. IRIS notes that SDMA methodology has not yet been standardized, that its recommendations are based on IDEXX Laboratories' proprietary method, and that it is not known whether other assays give equivalent results. Where possible, compare results measured by the same laboratory.
- Non-kidney causes. IRIS gives lymphoma in dogs and cats as an example where SDMA can rise without a fall in filtration, while creatinine is unaffected. The ISFM guidelines also caution that non-renal factors may affect SDMA.
- Breed. Healthy Birman cats tend to have higher SDMA and creatinine than other breeds, enough to put some healthy individuals outside laboratory ranges.
- Hydration and illness on the day. Because SDMA follows filtration, IRIS interprets it only in a hydrated, stable cat. A cat that was dehydrated or unwell when sampled should be retested.
- Hyperthyroidism. An overactive thyroid speeds up filtration and can keep SDMA low; eClinPath cites a study in which many hyperthyroid cats had SDMA below 10 µg/dL. A normal SDMA in an untreated hyperthyroid cat can therefore hide reduced kidney function.
- One result is a snapshot. IRIS uses a persistently raised SDMA, not a single reading, as evidence of early kidney disease.
Reading common SDMA results
These patterns come up often on feline reports. They describe what vets typically consider, not what your cat has.
| Result pattern | What it can mean | What vets often do |
|---|---|---|
| SDMA 15–17, creatinine normal, first time | Mildly above the limit. Could be early reduced filtration, mild dehydration or test variation; values just above the limit are the most likely to be false alarms. | Repeat SDMA and creatinine, typically a few weeks later, with a urinalysis |
| SDMA persistently above 14, creatinine normal | IRIS says a persistently raised SDMA may be used to diagnose early CKD (stage 1). If it stays above 18 while creatinine is below 1.6 mg/dL, IRIS suggests staging and treating as stage 2. | Urine specific gravity, urine protein, blood pressure; look for a cause; regular monitoring |
| SDMA high and creatinine high | Reduced filtration is likely if both persist in a hydrated cat. Staging uses creatinine with SDMA alongside; if SDMA stays above 25 µg/dL in a cat with stage 2 creatinine, IRIS suggests staging and treating as stage 3. | Confirm when stable and hydrated, then stage and substage (urine protein, blood pressure) |
| SDMA normal, creatinine high | A well-muscled cat, dehydration on the day or laboratory variation can raise creatinine alone. Early kidney disease is still possible, as no marker catches every case. | Recheck both when hydrated and fasted; urine specific gravity is key |
| SDMA rising after hyperthyroid treatment starts | Filtration returns toward the cat's true baseline once thyroid hormone is controlled, so some rise is expected; a larger rise can unmask kidney disease that was hidden. | Monitor kidney values, urine and blood pressure during treatment; adjust the plan if needed |
Trends matter as much as single numbers. IRIS counts creatinine or SDMA that keeps rising across serial samples as a sign of kidney change, even within the range, so keep every report and bring earlier results to appointments. For more on thyroid treatment and the kidneys, see cat thyroid (T4) results explained.
What vets usually do next
Exact plans depend on the cat, but after a high SDMA the follow-up usually includes some or all of these:
- Repeat SDMA and creatinine, typically a few weeks later, once the cat is eating, drinking and stable. IRIS bases staging on fasting values from a hydrated cat on at least two occasions; your vet will choose the timing.
- Run a urinalysis including USG, which shows how well the kidneys concentrate urine, ideally collected before any fluids are given. If the urine shows no infection or inflammation, a UPC measures protein loss.
- Measure blood pressure, usually more than once. The ISFM guidelines say it should be part of the routine evaluation of every cat with proven or suspected kidney disease.
- Check total T4 in older cats, because hyperthyroidism can hide kidney disease.
- Possibly image the kidneys with X-rays or ultrasound, which IRIS recommends for ruling out treatable problems such as kidney infection or a blocked ureter.
Your vet may also review any medicines your cat takes. Do not stop or change a medicine on your own because of a lab result; discuss it first.
Questions to ask your vet
- Was my cat well hydrated, and fasted, when the sample was taken?
- Which laboratory and method measured SDMA, and what is its reference range?
- Where is creatinine within its range, and how do both values compare with earlier results?
- What was the urine specific gravity, and do we need a UPC or a blood pressure check?
- Could thyroid disease, another illness or my cat's breed be affecting the result?
- When should we recheck, and what result would change the plan?
Frequently asked questions
What is SDMA in cats?
SDMA (symmetric dimethylarginine) is a small molecule released as cells throughout the body break down protein. The kidneys remove it from the blood, so its level rises when kidney filtration falls, which makes it a kidney function marker used alongside creatinine.
Is an SDMA of 15 bad for a cat?
On the IDEXX method the usual upper limit is 14 µg/dL, so 15 is mildly high. A single mildly high value with normal creatinine is a reason to recheck, typically a few weeks later together with a urine test, not a diagnosis of kidney disease.
What does high SDMA with normal creatinine mean in a cat?
It can be an early sign of reduced kidney filtration, especially in a thin cat whose low muscle mass keeps creatinine down. It can also reflect dehydration on the day, test variation or occasionally a non-kidney cause, so IRIS only uses a persistently raised SDMA as evidence of early kidney disease.
Is SDMA better than creatinine for cats?
SDMA is less affected by muscle mass and tends to rise earlier on average, but newer studies found the two perform similarly overall and SDMA gives more false alarms at the usual cut-off. Vets read them together, with urine specific gravity.
Can SDMA be high for reasons other than kidney disease?
Occasionally, yes. IRIS notes that lymphoma can raise SDMA without reduced filtration and that healthy Birman cats tend to run higher values. Dehydration also lowers filtration temporarily, and results from different laboratories and methods are not directly comparable.
Why did my cat's SDMA rise after hyperthyroidism treatment?
An overactive thyroid speeds up kidney filtration, which keeps SDMA and creatinine artificially low. Once thyroid hormone is controlled, filtration returns to the cat's true baseline, so some rise is expected and it sometimes reveals kidney disease that was hidden. Vets monitor kidney values during treatment for this reason.
Can a cat's SDMA go back to normal?
Yes. If the first result was pushed up by dehydration, a passing illness or ordinary test variation, a recheck can be within range. A value that stays high on repeat tests is the one that matters most.
Sources
- International Renal Interest Society. IRIS Staging of CKD (modified 2026) and Treatment Recommendations for CKD in Cats (2026). iris-kidney.com/iris-guidelines-1
- eClinPath, Cornell University College of Veterinary Medicine. SDMA. eclinpath.com/chemistry/kidney/sdma
- Sparkes AH, et al. ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease. Journal of Feline Medicine and Surgery. 2016;18(3):219–239. pmc.ncbi.nlm.nih.gov/articles/PMC11148907
- Cornell Feline Health Center. Chronic Kidney Disease. vet.cornell.edu