Understanding Your Kidney Lab Results: A Plain-English Guide

Why Kidney Labs Matter

Kidney disease often has no symptoms until significant damage has occurred. Blood and urine tests are the primary way doctors detect and monitor kidney problems. Understanding your results empowers you to be an active participant in your healthcare.

Serum Creatinine

What it is: A waste product from normal muscle metabolism. Healthy kidneys filter creatinine out of your blood.

Normal range: 0.6–1.2 mg/dL for most adults (varies by muscle mass, sex, and age).

What high values mean: Your kidneys may not be filtering efficiently. However, creatinine can be temporarily elevated from dehydration, intense exercise, high-protein meals, or certain medications.

Key point: Creatinine alone doesn't tell the full story. This is why doctors use eGFR (derived from creatinine) to get a more accurate picture of your kidney health.

eGFR (Estimated Glomerular Filtration Rate)

What it is: Calculated from creatinine, age, and sex. It estimates how much blood your kidneys filter per minute.

Normal: ≥90 mL/min/1.73m². Below 60 for 3+ months = CKD.

Why it matters: eGFR is the gold standard for assessing kidney function and determining CKD stage. Learn more about GFR →

BUN (Blood Urea Nitrogen)

What it is: Urea is a waste product from protein metabolism.

Normal range: 7–20 mg/dL.

What to know: BUN is generally less specific to kidneys than creatinine because it's also affected by your diet, hydration levels, or even liver and heart issues. Doctors often look at the BUN-to-creatinine ratio for extra diagnostic clues.

Potassium (K+)

Normal range: 3.5–5.0 mEq/L.

Why it matters for CKD: If kidneys are damaged, they may struggle to get rid of excess potassium. High potassium (hyperkalemia) is a serious concern because it can cause life-threatening heart rhythm problems.

If high: Limit high-potassium foods. Your doctor may prescribe potassium binders. Search kidney-friendly foods →

Phosphorus

Normal range: 2.5–4.5 mg/dL.

Why it matters: High phosphorus pulls calcium from bones (causing bone disease) and deposits calcium in blood vessels (causing cardiovascular problems). CKD stages 3+ often need phosphorus management.

Calcium

Normal range: 8.5–10.5 mg/dL.

CKD connection: Kidneys activate vitamin D, which helps absorb calcium. As kidneys fail, vitamin D drops, calcium drops, and the body pulls calcium from bones to compensate.

Albumin

Normal range: 3.5–5.5 g/dL.

What it indicates: Low albumin can signal nutritional problems, inflammation, or kidney/liver issues. In CKD, low albumin is associated with worse outcomes.

Hemoglobin

Normal range: 12.0–17.5 g/dL.

CKD connection: Your kidneys produce a hormone called EPO (erythropoietin) which tells your body to make red blood cells. As function declines, EPO production drops, leading to anemia. This is a very common complication for kidney patients.

Urine Tests

UACR (Urine Albumin-to-Creatinine Ratio)

Normal: <30 mg/g. Values 30-300 indicate microalbuminuria (early kidney damage). Above 300 indicates significant kidney damage.

UACR is one of the earliest ways to spot kidney damage, as it often detects problems well before your eGFR starts to drop.

UPCR (Urine Protein-to-Creatinine Ratio)

Normal: <150 mg/g. Measures total protein in urine. Elevated values may indicate glomerular disease.

How Often Should You Get Labs?

• No CKD, with risk factors: Annually
• CKD Stage 1-2: Every 6-12 months
• CKD Stage 3: Every 3-6 months
• CKD Stage 4: Every 1-3 months
• CKD Stage 5: Monthly or as directed