Decoding Albuminuria: What Low-Level Protein in Urine Really Means

In this episode of For Kidney’s Sake, consultant nephrologists Jeremy Levy and Andrew Frankel discuss albuminuria, focusing on the interpretation and management of low-level abnormal results. They explore how to distinguish between harmless fluctuations and early signs of kidney damage, clarify the coding system (A1, A2, A3), and explain why urine albumin-to-creatinine ratio (ACR) is such a valuable tool for early detection of kidney issues.

The conversation provides practical guidance for primary care teams, including when to repeat tests, when to refer, and how to reassure patients who are worried about ‘abnormal’ flagged results. They also emphasise the importance of annual kidney health checks for those at risk, especially patients with diabetes, hypertension, cardiovascular disease, or a family history of kidney disease.

3 Key Takeaways:

1. Know the ACR thresholds:
    
   • A1: <3 mg/mmol (normal) 
   • A2: 3–30 mg/mmol (moderately increased 
   • A3: >30 mg/mmol (severely increased, needs action).
     Severe proteinuria (>300 mg/mmol) requires urgent management.
2. Repeat and confirm abnormal results:
   Low-level abnormal ACRs (e.g., 5–20 mg/mmol) should be repeated to rule out temporary factors like exercise or fever. Persistent abnormal ACR—even with a normal eGFR—signals early kidney or vascular damage.
3. Manage risks early:
   Abnormal ACR requires blood pressure control (<130/80), consideration of ACE inhibitors/ARBs and SGLT2 inhibitors (especially in diabetes), and annual kidney health checks. Early optimisation can reverse or reduce albuminuria.

Resource Links:
NICE GUIDELINES [NG203] chronic kidney disease: assessment and management Overview | Chronic kidney disease: assessment and management | Guidance | NICE

Northwest London CKD guidelines for primary care Chronic kidney disease (nwlondonicb.nhs.uk)

The purpose of this podcast is to inform and educate health care professionals working in the primary care and community setting. The content is evidence based and consistent with NICE guidelines and North West Guidelines available at the time of publication.

The content of this podcast does not constitute medical advice and it is not intended to function as a substitute for a healthcare practitioner’s judgement.

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Transcript

Andrew Frankel
Hello, I'm Andrew Frankel. I'm a consultant kidney doctor working at Imperial College Healthcare NHS Trust.

Jeremy Levy
Hello again, I'm Jeremy Levy, I'm also a consultant nephrologist at Imperial Healthcare NHS Trust.

Andrew Frankel
Welcome today to another in our series of podcasts labelled For Kidney's Sake on low levels of albuminuria. Now in Northwest London, our primary care teams have been really excellent at improving the rates of sending off urine albumin creatinine ratios.

And we know this from the CVD Prevent data, and North West London currently is achieving this for 65% of all patients coded with CKD. And all 65% are getting their urinary ACR measured in the last year, which is above the national average of 49%, so that is really good. But of course we all, and that includes North West London, still need to do better.

But today, we want to consider more about what to do with the results, especially in those who could be described as having trivially abnormal results, but results that might still frighten your patient because of the red highlighting on the report or the label, which says abnormal. We need to remind ourselves of what is normal and abnormal, and also remind the listeners that everyone with risk factor CKD needs an annual ACR check.

And the commonest reasons, of course, are diabetes, hypertension, known cardiovascular disease, but equally important are those with a history of acute kidney injury, a family history of kidney failure or those with systemic diseases.

Jeremy Levy
Sorry, Andrew, and again, we're going to focus on that—what to do with the numbers, what to do with the results—and I'm going to start out by just reminding everybody what really is normal and abnormal and what the numbers actually mean.

And everything we're talking about is in UK or SI units, so if you're an American listener, you'll have to convert it into American units, but you're a minority so we'll stick with UK units.

So completely normal urine ACR, albumin-creatinine ratio, is less than 3 milligrams per millimole. Less than 3 is completely normal. 3 to 30 is moderately increased or moderately abnormal, and more than 30 milligrams per millimole is severely increased proteinuria. And that’s what gives us the coding: A1, A2, A3—that’s less than 3, 3 to 30, and more than 30.

And at this level, even though it's labeled as sort of severely increased, it's still very low levels proteinuria and there's a lot of variation. So at those levels, if you find one of those results, it still needs repeating.

Because in fact, very heavy proteinuria—and many of you will remember this term nephrotic syndrome, or you may vaguely remember it from medical school—nephrotic syndrome is very heavy proteinuria with edema, with low serum albumin levels, and nephrotic syndrome is an ACR of more than 300.

We often get emails from GPs saying the ACR 7 is abnormal—is it nephrotic? No, it's not nephrotic. Nephrotic is more than 300. So that range where we're coding is right down there at the lower end of detecting early kidney abnormalities.

So more than 300 is nephrotic. In that upper range of more than 70, but not nephrotic—so 70 to 300—that is high. Doesn’t need repeating straight away because it’s going to be still quite high, and that's a sort of threshold for needing referral to secondary care.

Andrew Frankel
So Jeremy, that's helpful indeed. So first of all, don't panic when you get a urine ACR result that is labelled abnormal, but say very low—5 to 10, or even an ACR of 45. You don't panic. You might need—well, you will need—to repeat the urine, and you will need, if it is repeated and confirmed, to take subsequent action. But none of this needs to be done urgently.

Jeremy Levy
That's right. And I'm just going to make one comment, Andrew, about this difference between the ACR, which is what GPs and practices are very good at measuring, and PCR—protein-creatinine ratio—because our audience may sometimes see those results.

And we're asking GPs to get used to one thing: the ACR. And we're doing that for several reasons. First of all, measure one thing, get used to the numbers and the ranges. But also because it's the earliest sign of damage in the glomeruli, the filtering units of the kidney. They leak the biggest protein in the blood, which is serum albumin, and the ACR test is very, very sensitive.

So that's why GPs are being asked, practices are being asked, to measure the ACR. And it's the first thing we would see in damage from diabetes and hypertension and vascular disease.

So for all those reasons, measuring the ACR is really, really important. And in primary care, that's what should be being used. In hospital kidney clinics, we do often measure a urine PCR—protein-creatinine ratio. And that’s for people where we know they've already got kidney disease, especially glomerular disease, and we know it's already quite heavy. Looking at trends in the PCR is useful. And some of our data on interventions in that group of patients is based around PCR.

But in primary care, just stick with ACRs. And if you see a number from hospital clinic, actually, in general, the ACR is about 70% of a PCR. So if you see a letter from a hospital that says PCR is 100, the ACR will be ballpark 70. But in primary care, just stick with urine albumin-creatinine ratios.

Andrew Frankel
Thanks, Jeremy, that's really helpful. And I'm going to now repeat again the numbers, but in relation to the coding so that everyone is clear.

So a urinary ACR of less than 3 is code A1 and, as you described, is normal or no albuminuria. 3 to 30 is A2 and more than 30 is code A3. Actually though, as you described, heavier proteinuria—which could be greater than 70 or, if you're looking at people who are nephrotic, would usually be greater than 300.

What about variation in this test, Jeremy? How does it vary from test to test?

Jeremy Levy
It varies a lot, actually, sadly, Andrew, as with lots of biological things. And I mean, it can really vary quite a lot, which is why there's a definite need to repeat it in that range that's up to about 70—certainly in that coding range—and repeating it again, not urgently. Don't phone the patient to come back tomorrow, but within two or three months.

Now, clearly, if you get two numbers, what are you going to do? You can use an average figure. But if a second number is completely normal, then they might not have it. Because lots of things can transiently increase the protein—it won’t be very high, but into that abnormal range. So for example, vigorous exercise or a recent fever could suddenly give you low-level albuminuria.

And that might be an ACR of 10 or 15, which suddenly gets flagged as abnormal. But when you repeat it a month later, it’s 1—completely normal. That was transient proteinuria and you don’t need to code that at all. So in that range up to 30 and certainly up to 70, repeat it and look at the second number. Over 70, it's going to be abnormal.

The last thing I was going to say, Andrew, is that morning-evening issue—because lots of the guidance says use a morning urine. The reality is if your patients come in the afternoon, just send the test. There is a little bit of a difference, but it's not greatly significant. Do the test, more importantly, than getting the patient to come back on a different occasion in the morning.

Andrew Frankel
Absolutely. Primary care find that pragmatic view so helpful. And I'm just going to throw this in, Jeremy—what about people who have got permanent catheters? Any comment about that?

Jeremy Levy
Really good point. So catheter will irritate the lining of the bladder wall and might give you low-level proteinuria. It will never be very high—it will not be 300—but it absolutely could be in that range of 10–15. And I think it's because the catheter is irritating the bladder wall, a few cells drop off, you often get leukocytes, and that might give you low-level proteinuria. It’s not a major worry, but it shouldn’t be very high.

Andrew Frankel
So one of the questions that we get a lot from primary care clinicians and also from patients is when people have a completely normal GFR—greater than 90—but they still have a urine ACR which is abnormal. They find it difficult to understand how this is possible and what's going on.

Jeremy Levy
So you're right—lots of emails and questions we get about that. And these are two different markers of kidney disease, and they don’t have to go hand in hand. The urine ACR, the albumin-creatinine ratio, is an early marker of some glomerular damage, but not the kidney function. While the eGFR is a marker of the kidney function and how well the kidneys clean the blood.

So very early damage in some glomeruli could lead to a rise in the urine albuminuria—the ACR—but your eGFR, your kidney function, is completely normal. And there are lots of reasons for that. The other glomeruli, for example, can compensate and some cope.

And then in some diseases—such as the best example would be minimal change nephrotic syndrome—the kidneys lose huge amounts of protein. The ACR can be 600, 700, but the eGFR remains more than 90. Completely preserved cleaning of the blood, but all those glomeruli are leaking protein. So definitely the two can be discordant. Don’t ignore an abnormal ACR, even if the eGFR is normal.

The transcript continues in this same format. Would you like me to include the remaining portion (from “And just to really emphasise that last point…” onwards) as well?