Kidney

Had a blood test this week, and the numbers are looking really good.

Normal kidney function is measured using two main values: eGFR (Estimated Glomerular Filtration Rate) and creatinine level. A good creatinine level is anywhere between 0.6 and 1.35 mg/dL (for females, up to 1.1 mg/dL), while eGFR should be above 60 mL/min/1.73 m².

For the past year, my creatinine level was hovering around 1.4 mg/dL, which put me in CKD (Chronic Kidney Disease) Stage 3A. This week’s tests, however, came back with a measurement of 1.2 mg/dL. After doing the math (more on that below), I’m now in CKD Stage 2. This puts me closer to having normally functioning kidneys.

Time to celebrate with a triple cheeseburger and a pint of whiskey!

Stages of CKD

Stage 1: eGFR ≥ 90
Stage 2: eGFR 60-89
Stage 3A: eGFR 45-59
Stage 3B: eGFR 30-44
Stage 4: eGFR 15-29
Stage 5: eGFR < 15 (or on dialysis)

My doctor won’t give me a specific eGFR number if it’s over 60, but here is the formula (and in Python) so we can calculate it:

Males:   eGFR = 141 × min(κScr, 1)α × max(κScr, 1)^-1.209 × 0.993^Age × 1.159 (if Black)
Females: eGFR = 144 × min(κScr, 1)α × max(κScr, 1)^-1.209 × 0.993^Age × 1.018 (if Black)

egfr.py

serum_creatinine = 1.2  # mg/dL
age = 44                # years
gender = "male"         # male

kappa = 0.9             # 0.7 for female
alpha = -0.411          # -0.329 for females

eGFR = 141 * min(serum_creatinine / kappa, 1)**alpha * max(serum_creatinine / kappa, 1)**(-1.209) * 0.993**age

print(eGFR)

What is eGFR / Creatinine?

eGFR is a measure of how well your kidneys are filtering waste from your blood. It’s calculated based on factors like your serum creatinine levels, age, sex, and race. The eGFR helps in assessing the stage of kidney disease and is expressed in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73 m²).

Creatinine is a waste product produced by muscle metabolism and is usually filtered out of the blood by the kidneys. The serum creatinine test measures the amount of creatinine in your blood and is used to evaluate kidney function. Higher levels of creatinine in the blood can indicate impaired kidney function.