Guides · Lab interpretation
Understanding your lab report
Every lab below explained in three lines: what it measures, what high vs low means, and one question to bring to your nephrologist. No jargon. No fear-tactic phrasing. Just what you need to walk into your next appointment confident.
See your eGFR with the eGFR calculator · plan your fluids with the fluid-budget tool · find your protein target with the protein calculator.
Serum creatinine (Creatinine)
A muscle waste product the kidneys filter out. Rises as kidney function falls.
~0.7–1.2 mg/dL in adults. Higher for those with more muscle (men, athletes); lower for older / smaller patients.
Reduced kidney function. Look at the trend, not a single value — a one-off high reading can come from dehydration or a high-protein meal.
Usually meaningless. Sometimes seen in malnutrition or low muscle mass — discuss with your dietitian.
Ask your nephrologist: "What is my eGFR from this creatinine, and how has it changed over the last year?"
Estimated glomerular filtration rate (eGFR)
How much blood your kidneys are filtering per minute. Calculated from creatinine + age + sex. Drives your CKD stage.
> 90 = stage 1, 60–89 = stage 2, 45–59 = stage 3a, 30–44 = stage 3b, 15–29 = stage 4, < 15 = stage 5 (kidney failure).
Generally good. > 90 with no urine protein = healthy.
CKD progression. Falling more than 5 per year is faster than typical aging — your nephrologist will want to identify the cause.
Ask your nephrologist: "Is my eGFR stable, or falling? If it's falling, what can we do to slow it?"
Blood urea nitrogen (BUN)
A protein waste product. Rises when kidneys can't clear it, but also when you eat a lot of protein or are dehydrated.
7–20 mg/dL.
Reduced kidney function — or just a high-protein day, dehydration, GI bleeding. Always interpret alongside creatinine.
Usually fine; can suggest low protein intake or liver issues.
Ask your nephrologist: "Is my BUN-to-creatinine ratio normal?"
Serum potassium (K (Potassium))
A mineral that controls nerve and muscle signals — including your heart rhythm.
3.5–5.0 mEq/L. CKD patients are sometimes allowed up to 5.5; > 5.5 is hyperkalemia and serious.
Hyperkalemia — risk of dangerous heart rhythm. Often from too much potassium-rich food, salt substitutes, ACEi/ARB meds, or missed dialysis.
Hypokalemia — also dangerous. Diuretics or vomiting/diarrhea are common causes.
Ask your nephrologist: "Is my potassium safe to stay on my current diet, or do I need to cut something?"
Serum phosphorus (P (Phosphorus))
Builds up in CKD because kidneys can't clear it. High levels pull calcium from bones, calcify arteries, and worsen cardiac risk.
2.5–4.5 mg/dL. Most renal patients target the lower half of that range.
Hyperphosphatemia. Driver of bone-mineral disorder. Check additive phosphorus in processed foods first, then diet, then binder dose.
Uncommon in CKD; can happen with malnutrition.
Ask your nephrologist: "Do I need a phosphate binder? At what dose, and with which meals?"
Serum calcium (Ca (Calcium))
Critical for bones, nerves, and muscle. Closely linked to phosphorus and PTH in CKD.
8.5–10.5 mg/dL (corrected for albumin).
Often from too much calcium-containing binder, vitamin D excess, or hyperparathyroidism. Increases vascular calcification.
Common in CKD; treated with active vitamin D or calcium carbonate.
Ask your nephrologist: "Are my calcium and phosphorus tracking together? Should we adjust my binder?"
Parathyroid hormone (PTH)
Hormone that controls calcium and phosphorus. Rises in CKD as kidneys lose the ability to make active vitamin D.
In CKD stages 3–5, targets are 2–9× normal (typically 130–600 pg/mL on dialysis).
Secondary hyperparathyroidism. Leads to bone disease, calcification. Treated with vitamin D analogs or calcimimetics.
Adynamic bone disease — bones don't remodel. Also bad. Discuss with your nephrologist.
Ask your nephrologist: "Is my PTH in the target zone for my stage?"
Hemoglobin (Hb)
Oxygen-carrying protein in red blood cells. CKD reduces erythropoietin, so anemia is very common.
12.0–17.5 g/dL in healthy adults. CKD targets often 10–11.5 g/dL.
Uncommon. Sometimes from overtreatment with ESA; raises clot risk.
Anemia of CKD. Cause for the fatigue you feel. Treated with iron + ESA (e.g. erythropoietin).
Ask your nephrologist: "Am I anemic? Should we check iron stores and consider an ESA?"
Serum albumin (Albumin)
The most abundant blood protein. Marker of nutrition, inflammation, and dialysis adequacy.
> 3.5 g/dL. On dialysis, > 4.0 is the long-term-survival target.
Usually fine; can indicate dehydration.
Hypoalbuminemia. Predicts worse outcomes on dialysis. Causes: malnutrition, inflammation, protein-losing kidney disease, liver issues.
Ask your nephrologist: "Is my albumin in the safe zone? If not, what should I change about my diet?"
Urine albumin-to-creatinine ratio (Urine ACR)
How much protein leaks into urine — a sensitive sign of kidney damage even before eGFR drops.
< 30 mg/g = normal. 30–300 = moderately increased (microalbuminuria). > 300 = severely increased.
Kidney damage present. ACR is one of the two pillars of CKD diagnosis (along with eGFR). Drives treatment intensity.
Good. < 30 mg/g means little to no kidney damage.
Ask your nephrologist: "How is my ACR trending? Should I be on an ACEi / ARB / SGLT2 to lower it?"
A note about ranges
The “normal” column is for the general population. CKD patients often have a different target — for example, hemoglobin target of 10–11.5 g/dL on dialysis is below the general adult range. Always interpret your lab against the range your nephrologist set for you, not the lab printout.
Not medical advice. If anything in your report worries you, call your nephrologist — don't wait for the next appointment.