The five stages of chronic kidney disease: a complete guide

When patients are first told they have chronic kidney disease, the most common questions I hear in clinic are the same: what stage am I at, what does that mean, and what happens next. The answer to all three depends on understanding the staging system properly, and that is what this article sets out to do.

Chronic kidney disease is one of those conditions that operates almost entirely under the radar until things have gone quite far. In Ireland, around one in ten adults has some degree of CKD, and the great majority do not know it. The condition is staged from 1 to 5 based on how well the kidneys are filtering blood, and understanding what stage you are in is the foundation of understanding what your care should look like.

This guide takes you through each stage in detail. What the numbers mean. What the tests show. What treatment is appropriate at each point. And what the realistic outlook is.

The measure used to stage CKD is the estimated glomerular filtration rate, or eGFR. It is calculated from a routine blood test that measures creatinine, a waste product produced by muscle metabolism. The body makes creatinine at a fairly steady rate, and the kidneys filter it out. If kidney function falls, creatinine rises and the eGFR falls. The eGFR is reported as millilitres per minute per 1.73 square metres, a unit of body surface area used to standardise the measurement.

There is a second component to staging that is sometimes overlooked: evidence of kidney damage. To be classified as CKD at the higher eGFR levels (stages 1 and 2), there must be other evidence that the kidneys are not entirely healthy. This is usually protein in the urine, sometimes blood in the urine, sometimes an abnormal scan finding, or sometimes a confirmed structural problem such as polycystic kidney disease. Without this other evidence, an eGFR above 60 in an otherwise healthy person is normal, not stage 2 CKD.

Stage 1 CKD means an eGFR of 90 or above with other evidence of kidney damage. Filtration is normal. The kidneys are clearing waste effectively. But something else, usually protein in the urine, is signalling that they are not entirely well. The focus at this stage is on identifying the underlying cause and treating it. A patient with diabetes who has developed mild protein leakage, for example, is at stage 1 CKD. The treatment focus is on tight glucose control, blood pressure optimisation, and starting kidney-protective medication such as an ACE inhibitor or ARB. Monitoring is annual at this stage. Most patients at stage 1 never progress to advanced disease.

Stage 2 CKD means an eGFR between 60 and 89 with the same supporting evidence of kidney damage. Filtration is mildly reduced. Again, the patient usually feels completely well. The principles are similar to stage 1: identify the cause, treat blood pressure, treat any underlying condition such as diabetes, and monitor periodically. Specialist input is helpful where the cause is unclear, where proteinuria is significant, or where the rate of decline appears faster than expected. Most patients at stage 2 also remain stable for many years with appropriate care.

Stage 3 is the most clinically significant stage to recognise because it represents the point at which active specialist input often starts to add real value. It is divided into two parts. Stage 3a means an eGFR between 45 and 59. Stage 3b means an eGFR between 30 and 44. The distinction matters because the risks and the management approach shift as eGFR falls below 45.

At stage 3a, treatment focuses on slowing the rate of decline. Blood pressure should be tightly controlled, with a target generally below 130/80. ACE inhibitors and ARBs are foundational. SGLT2 inhibitors are now recommended for most patients with significant proteinuria, regardless of whether they have diabetes. Cholesterol should be managed with a statin. Lifestyle measures including a Mediterranean-style diet, regular exercise, weight management, and smoking cessation matter. Monitoring is usually six to twelve monthly.

At stage 3b, the picture intensifies. Complications begin to emerge. Anaemia may develop as the kidneys produce less erythropoietin. Bone health requires attention as the kidneys lose their ability to activate vitamin D. Acidosis may begin to develop. The cardiovascular risk rises substantially: a patient with stage 3b CKD has cardiovascular risk comparable to a patient with established cardiovascular disease. Specialist referral is generally appropriate at this stage if it has not already happened. Monitoring is typically three to six monthly.

Stage 4 means an eGFR between 15 and 29. This is severe kidney impairment. The kidneys are doing less than a third of their normal work. Patients at this stage are under specialist nephrology care. Complications need active management: anaemia is treated, bone disease is addressed, electrolyte and fluid balance are monitored closely, and vaccinations including hepatitis B are arranged in case they are needed for dialysis access in future. Most importantly, planning for advanced therapies begins. Discussions about dialysis options (haemodialysis or peritoneal dialysis), about transplantation (including pre-emptive transplantation before dialysis is needed), and about conservative management are all part of care at this stage. Many patients with stage 4 CKD remain stable for years. Some progress. The goal of care is to delay progression as long as possible while preparing for whatever comes next.

Stage 5 means an eGFR below 15. This is kidney failure, sometimes called end-stage renal disease. Most patients at this stage will require dialysis or transplantation, although the exact timing depends on symptoms and complications rather than the number alone. Some patients with very gradual decline manage at very low eGFRs for some time. Others require dialysis sooner. The decision is individual.

There are several practical points worth understanding about staging.

The first is that staging describes function, not future. Many patients with stage 3 CKD remain at stage 3 for the rest of their lives. The stage is a snapshot, not a destiny.

The second is that the rate of change matters as much as the stage. A patient whose eGFR has been stable at 45 for ten years is in a very different situation from a patient whose eGFR fell from 75 to 45 in the last twelve months, even though both are at stage 3a.

The third is that the eGFR has limitations. It is an estimate, not a precise measurement. It can be affected by muscle mass, age, ethnicity, and recent illness. A single eGFR result should always be interpreted alongside repeat tests, the urine ACR, the blood pressure, and the overall clinical picture.

The fourth is that age affects how eGFR should be interpreted. A healthy 80-year-old will often have an eGFR of 60 to 70 simply because of age-related decline. This is not CKD on its own, although combined with other evidence of damage it may be.

The fifth is that staging is just the start of understanding kidney health. The cause of CKD matters. The rate of change matters. The level of proteinuria matters. The blood pressure matters. The overall cardiovascular profile matters. A complete picture requires more than the stage alone.

If you have been told you have CKD, the most useful questions to ask are: what stage am I at, what is the cause, what is the rate of change, what is my proteinuria, and what is my blood pressure. The answers shape your care.

For most patients, the message is genuinely reassuring. CKD is a long-term condition, but with the right care, most people live a normal lifespan with stable function. Specialist input is most useful at stages 3b, 4, and 5, but the foundations of good care (blood pressure control, kidney-protective medications, attention to cardiovascular risk, periodic monitoring) start from the moment CKD is diagnosed.

I see private patients at Blackrock Clinic, The Beacon Hospital, Bon Secours Dublin, the Hermitage Medical Centre, and St Vincent’s Private Hospital. If you would like a consultation about your kidney health, you or your GP can contact my secretary through drrorymcquillan.ie. Most patients are seen within two to three weeks of referral.