Dialysis typically becomes necessary when kidney function drops below about 15% of normal, but the exact timing depends more on how you feel and how your body is coping than on a single lab number. Most people start dialysis when their kidney filtration rate falls between 6 and 9 mL/min, a point where symptoms usually become difficult to manage with medication alone. Starting earlier than necessary doesn’t improve survival or quality of life, so the current medical consensus favors waiting until your body genuinely needs it.
Why Kidney Function Alone Doesn’t Decide
Kidney function is measured by a blood test called estimated glomerular filtration rate, or eGFR. Stage 5 kidney disease, the most advanced stage, begins at an eGFR below 15. But reaching that threshold doesn’t automatically mean you need dialysis right away. International guidelines from KDIGO, the most influential body in kidney care, specifically recommend basing the decision on symptoms, nutritional status, and how well medications are controlling complications rather than on a specific eGFR number.
Two people with the same eGFR can feel completely different. One person at an eGFR of 10 might have manageable symptoms and stable nutrition, while another at 12 might be losing weight, unable to keep food down, and retaining dangerous amounts of fluid. The second person needs dialysis sooner despite technically having better kidney function. This is why nephrologists evaluate the whole picture, not just one number on a lab report.
Early Start vs. Late Start: What the Evidence Shows
For years, there was debate about whether starting dialysis earlier (at a higher eGFR) would lead to better outcomes. The IDEAL trial, the largest randomized study to address this question, enrolled 828 patients with stage 5 kidney disease and assigned them to either early initiation (eGFR between 10 and 14) or late initiation (eGFR below 7, or when symptoms demanded it). The results were clear: survival was virtually identical between the two groups, with a hazard ratio of 1.04, meaning no meaningful difference. There were also no differences in cardiovascular events, infections, or dialysis complications.
What did differ was cost. Early starters spent more time on dialysis and used more healthcare resources without gaining any benefit. Based on this evidence, guidelines now recommend an “intent-to-defer” approach, meaning you and your nephrologist should plan to hold off on dialysis as long as symptoms and complications can be safely managed with medications and diet.
Symptoms That Signal It’s Time
As kidney function declines, waste products build up in the blood, a condition called uremia. The symptoms of uremia are what most commonly push the decision to start dialysis. They tend to creep in gradually, making them easy to dismiss at first, but they eventually become impossible to ignore.
Common uremic symptoms include:
- Persistent nausea and vomiting that interfere with eating
- Severe fatigue and drowsiness beyond what rest can fix
- Loss of appetite and unintentional weight loss, signs that your body can’t maintain its nutritional stores
- Intense itching across the body
- Muscle cramps and restless legs
- A metallic or unpleasant taste that changes how food tastes
- Difficulty concentrating, confusion, or memory problems, early signs of uremic encephalopathy
Nutritional decline is particularly important. If you’re losing lean muscle mass, your blood protein levels are dropping, and dietary changes aren’t helping, that progressive wasting is itself a strong reason to begin dialysis even if other symptoms are mild. The kidneys play a role in how your body processes protein, and once that system fails badly enough, dialysis is the only way to stop the downward spiral.
Emergencies That Require Immediate Dialysis
Some situations don’t allow for a gradual, planned start. Emergency dialysis is necessary when kidney failure creates life-threatening complications that can’t be controlled with medication.
Dangerously high potassium is one of the most urgent triggers. When blood potassium rises above 6.5 mmol/L, or reaches even lower levels but starts causing abnormal heart rhythms, dialysis may be needed within hours. The heart is extremely sensitive to potassium levels, and untreated hyperkalemia can cause cardiac arrest.
Severe metabolic acidosis, where the blood becomes too acidic because the kidneys can no longer regulate the body’s pH, is another emergency indication. So is fluid overload that resists diuretics, particularly when fluid backs up into the lungs and makes breathing difficult. Uremic pericarditis, an inflammation of the sac around the heart caused by toxin buildup, and uremic encephalopathy, which can progress from confusion to seizures, stupor, and coma, both demand urgent dialysis.
Planning Ahead: Access and Preparation
Even though the goal is to defer dialysis until it’s truly needed, preparation should begin well before that point. If you’re planning to do hemodialysis, you’ll need a vascular access point, and the preferred option is an arteriovenous (AV) fistula. This is a minor surgical procedure that connects an artery to a vein in your arm, creating a stronger vessel that can handle repeated needle access during dialysis sessions.
The catch is that a fistula needs time to mature before it can be used. Current guidelines recommend waiting at least four weeks after surgery before the first use, and full maturation typically takes one to four months, sometimes up to six. That means the surgery should ideally happen several months before you expect to need dialysis. Most nephrologists begin discussing access planning when eGFR drops below 20 to 25, well before stage 5, so there’s enough lead time.
If you’re considering peritoneal dialysis, which you do at home using the lining of your abdomen, a catheter needs to be placed surgically, and that also requires healing time before use. Whichever type you choose, the preparation timeline is a practical reason to stay closely connected with your kidney care team as your function declines.
What the Decision Actually Looks Like
For most people, the decision isn’t a single dramatic moment. It’s an ongoing conversation with your nephrologist over months or even years. As your eGFR approaches 15 to 20, your care team will start discussing what dialysis involves, which type fits your life, and when access should be created. You’ll have regular blood work tracking not just kidney function but potassium, acid-base balance, phosphorus, and nutritional markers like albumin.
At some point, usually when eGFR is in the range of 6 to 9, symptoms and lab trends will converge to make the need clear. You might notice that the nausea is constant, that you’ve lost significant weight without trying, or that swelling in your legs no longer responds to water pills. That’s when most people and their doctors agree: it’s time. The Canadian Society of Nephrology frames it well, noting that dialysis should start when uremia, fluid overload, nutritional decline, or metabolic problems become refractory to all other treatment, not at a predetermined number on a chart.
Some people with advanced kidney disease also choose conservative management, meaning they opt not to start dialysis at all, particularly older adults with multiple serious health conditions. This is a legitimate medical decision that involves focusing on symptom control and quality of life rather than extending time on dialysis. It’s a conversation worth having with your nephrologist if your overall health picture is complex.