What is the normal phosphorus lab value?

• A. 0.5-1.5
• B. 2.5-4.5
• C. 3.5-5.5
• D. 5.0-7.0

Answer: (B)

Phosphorus in the blood reflects bone metabolism and how well the kidneys, parathyroid hormone, and vitamin D work together to regulate mineral balance. The standard reference range for adults is about 2.5 to 4.5 mg/dL. This range is what most labs consider normal, so a value within it suggests typical phosphate homeostasis. Values higher than this can indicate kidney issues or hormonal imbalances affecting phosphate, while values lower than this can point to malnutrition or other disorders. The range 2.5–4.5 mg/dL is the best fit because it aligns with common adult reference intervals found in clinical practice.