Every month, your dialysis clinic hands you a sheet of paper covered in numbers, abbreviations, and ranges highlighted in red or yellow. Most of us nod politely, fold it up, and stuff it in a bag. I did that for months before I realized those numbers were trying to tell me something important — and learning to listen saved me a lot of pain.
This is your guide to reading CKD labs like a literate patient. Not a doctor, not a nurse — a patient who understands what their body is doing and can advocate for themselves.
The Foundation: GFR (Glomerular Filtration Rate)
GFR is the single most important number in kidney disease. It measures how well your kidneys filter waste from your blood, expressed in mL/min/1.73m². Think of it as a percentage — if your GFR is 30, your kidneys are working at roughly 30% capacity.
| GFR Range | CKD Stage | What It Means |
|---|---|---|
| 90+ | Stage 1 | Normal or near-normal function (with other signs of damage) |
| 60-89 | Stage 2 | Mildly decreased |
| 30-59 | Stage 3 | Moderately decreased — this is where most people get diagnosed |
| 15-29 | Stage 4 | Severely decreased — start planning for dialysis or transplant |
| Below 15 | Stage 5 | Kidney failure (ESRD) — dialysis or transplant needed |
Don't panic over a single GFR reading. The trend matters more than any single number. Ask your doctor to show you your GFR over the last 6-12 months. A slow, steady decline is very different from a sudden drop.
Creatinine: The Number Everyone Knows
Creatinine is a waste product from muscle metabolism. Healthy kidneys filter it out efficiently. When kidney function drops, creatinine rises. For dialysis patients, creatinine is typically elevated (often 8-14 mg/dL or higher) and that's expected — it's not the same alarm bell it would be for someone with functioning kidneys.
Normal range: 0.7-1.3 mg/dL (non-dialysis)
Dialysis patients: Your pre-dialysis creatinine will be elevated. What matters is the pattern and whether it's stable between treatments.
BUN (Blood Urea Nitrogen)
BUN measures urea, another waste product. It rises when kidneys can't remove it. For dialysis patients, BUN is checked pre- and post-treatment to calculate your Kt/V (dialysis adequacy).
Normal range: 7-20 mg/dL
Dialysis patients: Pre-dialysis BUN of 50-80 is common. Post-dialysis should drop significantly — that reduction ratio is what tells your team how effective your treatment was.
Potassium: The Silent Danger
I call potassium the "silent guardian" because keeping it in range protects your heart, but it gives you almost no warning when it's dangerously high. There's no reliable symptom for hyperkalemia until your heart rhythm is already affected.
Target: 3.5-5.5 mEq/L
- Below 3.5: Hypokalemia — weakness, cramps, irregular heartbeat
- 3.5-5.5: Safe zone
- 5.5-6.0: Elevated — dietary adjustments needed
- Above 6.0: Dangerous territory — risk of cardiac arrest
Salt substitutes (like "NoSalt" or "Nu-Salt") use potassium chloride instead of sodium chloride. I was proudly avoiding sodium while accidentally spiking my potassium. Read every label. The danger is in the substitutions.
Phosphorus: The Long Game
Phosphorus doesn't make you feel terrible immediately when it's high. It works slowly, depositing calcium-phosphate crystals in your blood vessels, joints, and organs. High phosphorus over months and years causes vascular calcification, bone disease, and itching that will drive you insane.
Target: 3.5-5.5 mg/dL
The key to managing phosphorus is taking your binders with food — not before, not after. The binder needs to physically encounter the phosphorus in your stomach to bind it. Think of it like a sponge that has to be in the water to absorb anything.
Albumin: Your Nutritional Report Card
Albumin measures protein in your blood and is the best single indicator of your nutritional status on dialysis. Low albumin is one of the strongest predictors of poor outcomes in dialysis patients — more than almost any other lab value.
Target: 4.0 g/dL or higher
- Above 4.0: Well-nourished
- 3.5-4.0: Borderline — increase protein intake
- Below 3.5: Malnourished — significant concern
Dialysis patients need more protein than healthy people, not less. The treatment itself strips protein from your blood. Aim for 1.0-1.2 grams of protein per kilogram of body weight daily. That's roughly 8-10 ounces of meat, fish, or poultry per day for most adults.
Hemoglobin: Your Energy Level
Kidneys produce erythropoietin (EPO), the hormone that tells your bone marrow to make red blood cells. When kidneys fail, EPO production drops, and you become anemic. This is why fatigue is such a universal experience in CKD.
Target: 10-12 g/dL for dialysis patients
Most dialysis patients receive EPO-stimulating agents (Epogen, Aranesp, Mircera) to boost red blood cell production. If your hemoglobin stays low despite treatment, iron stores are usually the bottleneck — ask about your ferritin and TSAT levels.
Calcium and PTH: The Bone Connection
These two work together. When phosphorus is high and calcium is low, your parathyroid glands go into overdrive, pumping out PTH (parathyroid hormone) to pull calcium from your bones. Over time, this causes renal osteodystrophy — bones that become weak, brittle, and painful.
Calcium target: 8.4-10.2 mg/dL
PTH target: 150-600 pg/mL (dialysis patients; yes, the range is much wider than for healthy people)
Putting It All Together
Here's the real secret: these numbers don't exist in isolation. They're a system, each one connected to the others like a web. High phosphorus drives high PTH which pulls calcium from bones. Low albumin suggests poor nutrition which worsens anemia. Inadequate dialysis (low Kt/V) leaves toxins that suppress appetite which drops albumin further.
When you look at your lab sheet, don't just check if numbers are in range. Look for the relationships between them. That's where the real understanding lives.
"The measure of intelligence is the ability to change." — Albert Einstein
Your labs are a conversation between your body and your treatment. Learn the language, and you become an active participant in your own survival.
Action Steps
- Ask for a copy of your labs every month — it's your legal right
- Track trends over time, not just single readings — a simple notebook or spreadsheet works
- Circle anything out of range and ask your care team about it at your next visit
- Understand the connections — if one number is off, look at what else might be affected
- Bring questions — the best patients are the ones who ask the most questions