Acute Kidney Injury is a sudden drop in kidney filtering over hours to days. Blood testing looks for that loss by measuring creatinine (muscle waste), estimating GFR (eGFR), measuring blood urea nitrogen (BUN), and calculating the BUN/creatinine ratio to hint at cause and severity. Superpower tests your blood for Creatinine, eGFR, BUN, and the BUN/Creatinine Ratio. These markers rise or fall as kidneys fail to clear waste and regulate fluid and acid-base balance. The panel complements clinical findings like urine output and blood pressure but often gives the earliest, objective signal that the kidneys are under stress.

AKI can be silent but life-threatening. Early shifts in creatinine, eGFR, BUN, and the BUN/creatinine ratio flag reduced filtration and perfusion before symptoms are obvious. Testing is critical if you’re acutely ill, dehydrated, recently had surgery, received IV contrast, or started kidney-stressing medicines. If you have diabetes, hypertension, heart failure, or known kidney disease, results guide triage, fluid status assessment, and medication decisions. In plain terms: it tells us how hard your kidneys are working right now, whether the problem is low flow (prerenal) or intrinsic injury, and how quickly it’s changing.

Yes. With Superpower, our team member can organize a blood draw in your home.

For suspected AKI, test promptly and trend the change—typically repeat within 24–48 hours, and sooner if levels are rapidly changing or urine output falls. After exposure to potential kidney stressors (major illness, surgery, IV contrast, new nephrotoxic drugs), check within the first 24–72 hours. If you’re stable and low risk, these markers are usually included with routine annual labs. If you have chronic kidney disease or high risk, monitoring is more frequent around clinical events. In AKI, the trajectory over time matters more than a single value.

Hydration and perfusion status strongly sway BUN, creatinine, and their ratio. Muscle mass, recent strenuous exercise, and high meat or creatine intake raise creatinine independent of kidney function. Catabolic states, gastrointestinal bleeding, corticosteroids, and tetracyclines elevate BUN. Medications that reduce filtration or alter tubular secretion—NSAIDs, ACE inhibitors/ARBs, diuretics, trimethoprim, cimetidine—can raise creatinine. Recent iodinated contrast can trigger AKI. Pregnancy lowers baseline creatinine. Age and sex affect eGFR estimates, and eGFR is unreliable when kidney function is changing rapidly (non–steady state).

No special fasting is required for Creatinine, eGFR, BUN, or the BUN/Creatinine Ratio. Aim for usual hydration; avoid deliberate over- or under-drinking before the draw. Skip heavy meat meals, protein shakes, or creatine supplements the day before, and avoid strenuous exercise for 24 hours, as these can transiently raise creatinine and BUN. If safe, note the timing of medications that affect creatinine secretion (for example, trimethoprim or cimetidine) and any recent IV contrast. A morning sample helps with consistency, but timing is less critical than getting tested promptly when AKI is suspected.

Yes, but mostly at the margins. Hydration status and protein intake can shift BUN and the BUN/creatinine ratio; muscle mass and supplements can change creatinine. Avoiding kidney stressors (nephrotoxins, dehydration) lowers AKI risk. That said, abnormal results usually reflect true kidney physiology, not just lifestyle. Short-term changes can move numbers without fixing the cause. If values are outside your baseline or trending worse, the priority is medical evaluation and addressing the underlying process.

Look at the change from your baseline and the pace. A creatinine rise ≥0.3 mg/dL in 48 hours or ≥1.5× baseline within 7 days meets AKI criteria (KDIGO). eGFR >90 is normal; <60 suggests impaired filtration, but eGFR is less accurate during acute changes. Typical BUN is about 7–20 mg/dL; higher values reflect reduced clearance or increased production. A BUN/creatinine ratio of ~10–20 is usual; >20 suggests prerenal states (low kidney blood flow), whereas a lower ratio with rising creatinine points toward intrinsic kidney injury or low urea production. Always interpret alongside symptoms and urine output.