Does a creatinine of 1.46 mg/dL in an 84-year-old man suggest reduced kidney function?

An age-related decline in renal reserve makes reduced filtration more consequential in older adults, but the immediate clinical signal here is the creatinine value interpreted with age and sex.

Clinical interpretation

• In an 84-year-old man, serum creatinine 1.46 mg/dL corresponds to a 2021 CKD-EPI creatinine eGFR of approximately 48 mL/min/1.73 m². This is below 60 mL/min/1.73 m² and would be in the G3a range if it persists.
• Therefore, lack of a laboratory-reported eGFR should not be reassuring: this value appropriately raises concern for reduced kidney filtration.
• One result does not establish chronic kidney disease (CKD). CKD requires reduced eGFR or another kidney abnormality to be present for at least 3 months. Repeat creatinine/eGFR testing and urine albumin-to-creatinine ratio help establish chronicity and refine risk.

Aging and renal mechanisms

• Renal functional reserve—the capacity to increase GFR after a protein or amino-acid load—generally declines with advanced age. Aging is associated with nephron loss, glomerulosclerosis, and substantially fewer nonsclerosed glomeruli in adults aged 70–75 than in young adults.
• This is a population trend rather than an inevitability: some healthy older adults retain measurable reserve, including approximately a 17% amino-acid-stimulated GFR increase in one small inulin-clearance study.

Practical considerations

• Creatinine-based eGFR can be misleading during acute illness or non–steady-state kidney function. Low muscle mass, frailty, malnutrition, or sarcopenia can reduce creatinine generation and make creatinine-based eGFR overestimate true filtration.
• When precision would affect management, cystatin C–based or combined creatinine–cystatin C eGFR can corroborate the estimate; measured GFR may be useful for high-consequence decisions.

Bottom line

• Creatinine 1.46 mg/dL in this 84-year-old man is a meaningful concern for reduced kidney function (estimated eGFR ~48), warranting follow-up rather than attribution to normal aging alone.