Stage 3: Moderately reduced

What it means

Stage 3 is the most common stage we see in clinic, and the stage at which most patients are first referred to nephrology. The kidneys are noticeably working harder than they used to, and certain lab values that were normal at Stage 1 and 2 start to drift.

We split Stage 3 into two bands because the picture and the management differ between them.

Stage 3a — GFR 45 to 59

At 3a, most people still feel completely well. Some notice mild fatigue or waking up at night to urinate (nocturia). Blood work may show the earliest hints of mineral-bone changes: phosphorus drifting up, parathyroid hormone (PTH) starting to rise. Hemoglobin may dip a little. Often these are subtle enough that they’re only obvious because we’re looking.

Stage 3b — GFR 30 to 44

At 3b, lab changes are more obvious. Potassium can trend higher. Bicarbonate may drop, meaning the blood becomes slightly more acidic (metabolic acidosis). Bone-mineral changes accelerate. Anemia becomes meaningfully more likely, and many patients begin to feel fatigued, notice mild ankle swelling, or experience appetite changes.

What your care team focuses on

• All the basics from earlier stages — cause-directed treatment, blood pressure, ACE/ARB, SGLT2 inhibitors when appropriate, cardiovascular risk reduction.
• Bone and mineral balance. If phosphorus is elevated, a binder (a pill taken with meals that traps phosphorus before your body absorbs it) may be added. Vitamin D supplementation and PTH monitoring become routine.
• Metabolic acidosis. If serum bicarbonate drops below about 22 mEq/L, oral bicarbonate is often added. Treating acidosis has been shown in studies to slow CKD progression.
• Anemia workup. Iron studies first. If iron is low, replenish it; if iron is fine but hemoglobin stays low, an erythropoiesis-stimulating agent (ESA) may be considered.
• Nutrition becomes specific. Most patients see a registered renal dietitian. The focus is on sodium, watching phosphorus additives, and right-sizingprotein — not severely restricting it. The old “low-protein diet” approach has nuanced into balanced, individualized guidance.
• Potassium awareness.Not every Stage 3 patient needs restriction. Many do not. Lab trends, current medications, and the dietitian’s individualized plan guide what (if anything) to change.
• Cardiovascular protection. Statistically, Stage 3 patients are more likely to have a cardiac event than to progress to dialysis. Blood pressure, lipids, smoking, and diabetes management deserve more attention here, not less.
• Education about future options. Not to alarm — to give you time. If progression ever happens, having heard about transplant and dialysis modalities calmly in advance makes those decisions easier.

Questions patients often ask

Stage 3 is where active management makes the biggest difference. Showing up for the visits, taking the medications as prescribed, and working the nutrition plan are quiet, daily acts that protect the years ahead.