Normal range: 2.5 - 7.5 mmol/L

Key roles of urea:

• Non-toxic waste product of protein metabolism
• Urine-concentrating mechanism

Causes of high urea:

• AKI
• Dehydration
• GI bleed - hypovolaemia, digested RBC can release more urea
• high protein diet
• CCF

Causes of low urea:

• Poor oral intake
• Liver disease
• Haemodilution