Scale Calibration: Requirements of the FDA

The GMP regulations do not provide any concrete specifications for the calibration of weighing instruments. They refer to suitable measuring and weighing ranges and the required accuracy. Regular maintenance and calibration are also required. This applies to both the EU and the USA (21 Code of Federal Regulations (CFR) 211).

So how can these general formulations be interpreted?

A current Warning Letter referring to the CFR provides helpful information on this. It criticizes that necessary calibrations were neither performed nor recorded. In particular, one scale was calibrated with a weight that was not representative of the quantities to be weighed on it. The weight with which the scales were regularly checked was last calibrated in 2008.

The company's reply to the FDA stated that the scales had been taken out of service and would be calibrated annually in the future.

FDA's response 

For the FDA, this statement was inadequate. They expect a review of the entire instrument calibration and the following measures to be considered:

• A review of the products distributed that may have been affected by inadequate calibration.
• A plan to inform customers affected by inadequate scale calibration
• CAPA measures to ensure oversight of the devices in routine operations. This control is intended to ensure that inadequate instrument performance can be detected quickly, repairs can be carried out, full maintenance performed and instrument calibration conducted.  

You can find the complete Warning Letter on the FDA website.