SDMA in cats: what 14, 18, and 25 actually mean

Articles · Lab Values

If a number like SDMA suddenly appeared on your cat’s bloodwork with an asterisk next to it, you are not alone in feeling thrown. This guide explains what SDMA measures, what common values such as 14, 18, and 25 generally mean, and why it is often the first kidney marker to move.

What is SDMA on my cat’s blood test?

SDMA (symmetric dimethylarginine) is a marker of kidney filtration measured on many feline blood panels. As cells throughout the body turn over, they release SDMA, and healthy kidneys clear it from the blood. When filtration declines, SDMA accumulates and the value rises, which is why it is used to flag early kidney changes.

SDMA entered routine veterinary practice in 2015 and is now common on senior-cat panels. Unlike older markers, it is relatively unaffected by muscle mass, which matters in older, leaner cats whose creatinine can look falsely reassuring.

What do SDMA cat levels like 14, 18, and 25 actually mean?

In broad terms, an SDMA under about 14 µg/dL is considered within the reference range, the upper teens are a “watch and recheck” zone, and values in the mid-20s point toward more established kidney involvement. These are general reference points, not a diagnosis, and your lab’s printed range and your cat’s trend always come first.

Here is the plain-English read most clinicians use, anchored to the International Renal Interest Society (IRIS Staging of CKD, 2023) feline SDMA bands:

• Around 14 µg/dL or below: within range at this snapshot. No kidney concern is flagged from SDMA alone.
• Roughly 14 to 18 µg/dL: mildly elevated. This is a recheck zone, since transient dehydration can nudge it up. A repeat test in a few weeks helps separate a blip from a trend.
• Persistently above 18 µg/dL: the kidney concern threshold. IRIS notes that if SDMA stays above 18 in a cat whose creatinine is still under 1.6 mg/dL, the cat is generally staged and managed as IRIS Stage 2 rather than Stage 1.
• Roughly 18 to 25 µg/dL and higher: corresponds to the IRIS Stage 2 to 3 range, where monitoring and a management plan usually become the focus.

Why does SDMA rise before creatinine?

SDMA is more sensitive to early filtration loss than creatinine. According to Hall and colleagues in the Journal of Veterinary Internal Medicine (2014), SDMA can increase when about 25% of kidney function is lost, while creatinine often stays within range until roughly 75% of function is gone. That gap is why SDMA frequently rises months before creatinine does.

That early window is the whole point of the test. Catching kidney change earlier means you and your vet can start monitoring water intake, weight, diet, and phosphorus sooner, when there is more function left to protect. For the bigger picture, see our overview of what SDMA is and our guide for CKD cats.

Should one elevated SDMA worry me?

Not on its own. A single mildly high SDMA is a prompt to recheck, not a verdict, because dehydration and normal day-to-day variation can move it. IRIS staging is deliberately built on persistent changes confirmed on more than one stable sample, so the recheck is part of the process, not a sign something was missed.

Interpret SDMA alongside the rest of the picture: creatinine, BUN, phosphorus, urine specific gravity, body weight, and how your cat is acting at home. A high SDMA with dilute urine and rising creatinine reads very differently from an isolated borderline value in a well, hydrated cat.

What can make SDMA go up besides kidney disease?

SDMA is a fairly specific kidney marker, but it is not immune to other influences, which is why a single value is interpreted in context. Temporary changes in hydration and the normal day-to-day biological variation of any blood test can move it, and a marginally high result on one sample does not always repeat on the next. That is precisely why the recheck exists.

Things worth keeping in mind:

• Dehydration can transiently raise SDMA along with other kidney markers, so a cat tested after skipping water may read higher.
• Normal biological variation means any lab value wobbles a little between draws; a small change may be noise rather than a trend.
• Other illness elsewhere in the body can sometimes nudge results, so vets weigh SDMA against the whole clinical picture.

None of this makes SDMA unreliable. It just means the pattern over repeated tests is more trustworthy than any one figure.

What does an SDMA value not tell me?

An SDMA number tells you about filtration, not about why filtration changed or how a cat will feel day to day. It does not name a cause, it does not replace urine testing or blood pressure checks, and it does not on its own set a prognosis. It is one informative piece of a larger kidney picture, best read alongside the rest.

To round out the picture, your vet may add:

• A urinalysis, including urine concentration (specific gravity) and protein, which can shift early in kidney disease.
• Blood pressure, since hypertension and kidney disease often travel together.
• Phosphorus and other chemistry, which help with staging and management decisions.

Seen this way, SDMA is a sensitive smoke detector: valuable for catching a problem early, but not the full diagnosis on its own.

What should I ask my vet about my cat’s SDMA?

Focus questions on context and trajectory rather than a single value. Good ones include: how does this SDMA compare with last time, what is my cat’s IRIS stage when you combine SDMA with creatinine and urine concentration, and what would change the plan. Those questions turn a scary number into a clear next step.

Other useful questions to bring:

• Is this a one-time recheck, or are we now monitoring on a schedule?
• What home signs (drinking, urinating, appetite, weight) should I track between visits?
• Would a urinalysis or blood pressure check add useful information right now?

How can I keep an eye on the trend at home?

You do not need to interpret SDMA yourself, you need to see how it is moving. Pawtient AI’s blood-test scan and trends view lets you photograph each report so SDMA and the related kidney markers are captured and charted over time, so the next conversation with your vet starts from a trend line instead of a single page. Our lab value translator can also put a value in plain language.

Pawtient AI is an AI assistant and second opinion, never a diagnosis — always consult your veterinarian.

Sources

• International Renal Interest Society. IRIS Staging of CKD (modified 2023). iris-kidney.com
• Hall JA, et al. Comparison of serum concentrations of symmetric dimethylarginine and creatinine as kidney function biomarkers in cats with chronic kidney disease. Journal of Veterinary Internal Medicine, 2014.
• IDEXX Laboratories. SDMA Testing for Cats and Dogs — interpretive resources. idexx.com

By Pawtient AI Editorial Team. Educational content reviewed against published veterinary guidelines (IRIS, AAHA, WSAVA, ACVIM, AAFP). Not a substitute for veterinary care.