Protein Binding Free Fraction (fu) Calculator

Calculate the unbound drug fraction (fu = free concentration / total concentration) to assess clinically relevant drug exposure, adjust therapeutic drug monitoring interpretation, and identify displacement interactions.

Weight
Height
Clinical Guidance

BMI is a screening measure of body size, not a direct measure of body fat. The standard WHO categories are underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30).

BMI can overestimate body fat in athletes with high muscle mass and underestimate it in older adults with low muscle mass. Interpret it alongside waist circumference and clinical context rather than as a standalone diagnosis.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.
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How to Use

Enter the values for the scenario you are assessing. Calculate the unbound drug fraction (fu = free concentration / total concentration) to assess clinically relevant drug exposure, adjust therapeutic drug monitoring interpretation, and identify displacement interactions. Use the protein binding fu result to inform your calculation.

Frequently Asked Questions