21 CFR 211.103 - Calculation of Yield

What it says

Actual yields and percentages of theoretical yield must be calculated at the completion of appropriate phases of manufacturing, processing, packaging or holding, with any calculated yield falling outside established limits investigated.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• Yield calculation is a built-in check that a batch's actual material balance is consistent with what the process is expected to produce, functioning as an early signal of a potential process problem or, in some historical cases, of diversion.
• A yield discrepancy outside the established limit is a required investigation trigger regardless of whether the batch otherwise passes all release testing, since the discrepancy itself signals something unexplained occurred during processing.
• Yield limits must be scientifically established based on the specific process's normal variation, not set arbitrarily wide simply to avoid triggering frequent investigations.

What FDA inspectors look for

• Whether yield is calculated and documented at each appropriate manufacturing phase, not just once at the very end of the process.
• Whether yield discrepancies outside established limits are genuinely investigated, with a documented root cause conclusion, rather than simply noted and accepted.
• Whether yield limits themselves have a documented scientific or historical basis appropriate to the specific process.

Related regulations