👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Physiological Adaptation🔖 Free to read, print, and share
Also known as: kidney function · renal labs · BUN creatinine · BUN/Cr ratio
💡
Use this quick-reference guide to spot, treat, and prevent Creatinine and BUN on the NCLEX. Keep it handy during review and on exam day!
🩺
📒 The 1-minute cheat sheet
🧪 Values
Creatinine 0.6-1.2 mg/dL
BUN 10-20 mg/dL
BUN:Cr ratio ~10-20:1
📌 Creat
Best kidney function indicator
Not affected by diet/hydration
↑ = renal impairment
📌 Bun
↑ dehydration, GI bleed, ↑protein
↓ overhydration, liver disease
🚩 Report
↑Cr → hold nephrotoxic drugs
Hold contrast, metformin
📚 Creatinine and BUN — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what must be reported, and what to teach.
BUN and creatinine are the primary blood markers of kidney function. Creatinine is the more reliable indicator because it is produced steadily by muscle and cleared by the kidneys, while BUN is influenced by hydration, diet, and bleeding. A rising creatinine signals declining renal function and the need to adjust nephrotoxic and renally cleared medications.
🔑
Key points
Understand these first
Creatinine is a more specific marker of kidney function than BUN.
An elevated BUN with a normal creatinine often reflects dehydration rather than kidney disease.
A BUN-to-creatinine ratio above about 20 to 1 suggests a prerenal cause such as dehydration.
Rising creatinine often requires dose reduction or holding of renally cleared and nephrotoxic drugs.
GFR estimated from creatinine stages chronic kidney disease severity.
Many contrast studies and nephrotoxic antibiotics require checking renal function first.
✅
Nursing priorities
What to do, in order
Monitor intake, output, and daily weights to evaluate fluid status and kidney perfusion.
Review medications for nephrotoxic agents and renally cleared drugs needing adjustment.
Ensure adequate hydration when a prerenal cause such as dehydration is suspected.
Hold or question nephrotoxic drugs and contrast in patients with rising creatinine.
Trend creatinine and GFR to detect worsening renal function early.
🚩
Red flags — report now
Escalate immediately
A rapidly rising creatinine with decreasing urine output signals acute kidney injury and must be reported.
Urine output under 30 mL per hour is a sign of inadequate kidney perfusion requiring escalation.
Never give nephrotoxic drugs or contrast without checking renal function in an at-risk patient.
🧪
Labs & values
Numbers to know
BUN 10-20 mg/dL
Creatinine 0.6-1.2 mg/dL
BUN/creatinine ratio 10-20:1
GFR > 90 mL/min (normal)
Urine output > 30 mL/hr (adequate)
🗣️
Patient teaching
What patients must know
Stay well hydrated unless fluids are restricted, and tell providers about all medications and NSAID use.
Attend follow-up labs to monitor kidney function, especially with diabetes or high blood pressure.
❓ Creatinine and BUN: NCLEX FAQs
What are the priority nursing interventions for Creatinine and BUN?
Monitor intake, output, and daily weights to evaluate fluid status and kidney perfusion. Review medications for nephrotoxic agents and renally cleared drugs needing adjustment. Ensure adequate hydration when a prerenal cause such as dehydration is suspected. Hold or question nephrotoxic drugs and contrast in patients with rising creatinine.
What are the warning signs of Creatinine and BUN a nurse must report?
A rapidly rising creatinine with decreasing urine output signals acute kidney injury and must be reported. Urine output under 30 mL per hour is a sign of inadequate kidney perfusion requiring escalation. Never give nephrotoxic drugs or contrast without checking renal function in an at-risk patient.
What do I need to know about Creatinine and BUN for the NCLEX?
Creatinine is a more specific marker of kidney function than BUN. An elevated BUN with a normal creatinine often reflects dehydration rather than kidney disease. A BUN-to-creatinine ratio above about 20 to 1 suggests a prerenal cause such as dehydration. Rising creatinine often requires dose reduction or holding of renally cleared and nephrotoxic drugs.
What patient teaching is important for Creatinine and BUN?
Stay well hydrated unless fluids are restricted, and tell providers about all medications and NSAID use. Attend follow-up labs to monitor kidney function, especially with diabetes or high blood pressure.
✨
Quick Tip
Creatinine is a more specific marker of kidney function than BUN.