Definition: AUC (area under the curve) is the area under a graph of drug level against time. It sums up total exposure to a dose in one number. The FDA uses AUC to describe the extent of absorption, while Cmax and Tmax describe the rate.
The kinds of AUC you will see
FDA guidance names three. AUC0-t runs from the dose to the last time point with a measurable level. AUC0-INF extends that to infinity by estimating the tail. AUC0-TAU covers one dosing interval at steady state, where TAU is the length of the interval, such as one week.
Units combine level and time, for example ng·h/mL. A tall, narrow curve and a low, wide curve can have the same AUC. That is why labels report AUC and Cmax together.
Worked example: reading AUC changes on labels
Two label figures, worked through
- The Macrilen label says a liquid meal lowered macimorelin AUC by 49% and Cmax by 55%. If AUC was 100 units fasting, it would be 100 × (1 − 0.49) = 51 units after the meal.
- The Ozempic label gives average steady-state levels of about 65 ng/mL on 0.5 mg weekly and 123 ng/mL on 1 mg weekly.
- An average level times the length of the interval gives the area. For one week (168 hours): 65 × 168 = 10,920 ng·h/mL, and 123 × 168 = 20,664 ng·h/mL.
- 20,664 ÷ 10,920 = about 1.9. Doubling the dose came close to doubling exposure, which matches the label saying exposure rises in proportion to dose.
These are averages from study groups. Individual numbers vary with body size, kidney and liver function and the product itself.
Common mix-ups
- AUC is not the peak. It is the whole area, so it reflects both how high and how long.
- AUC on a label is a group average. It is not something a single blood test can give you.
Read more on Dose Track: Ozempic guide
General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.