The FDA Warning Letter is an official notification from the FDA that identifies serious violations of the regulations. A warning letter will be issued by a senior FDA official after reviewing the inspector's report. The warning letter was deemed an escalation of observations by 483.
You may also know about FDA warning letters via https://wizmed.com/fda-warning-letters.
The most common reasons for FDA warning letters are:
Inadequate written procedures.
Failure to follow written procedures.
Lack of evidence that regulations are met with adequate documentation.
Warning letters are usually sent in person to ensure they are reviewed and processed promptly. Like FDA 483 surveillance, FDA warning letters require a written response within a maximum of 15 days. If the reasons for the FDA warning letter are so severe, the FDA may extend the deadline. You must correct the violations that are described in the FDA warning letter.
A warning letter was issued. Anyone can find out that a letter has been issued to the company. We've even heard competitors use corporate warning letters as a negative example of why potential customers should choose their own company over competitors.
As with 483 observations, the warning letter processing can be very expensive. Receiving warning letters can greatly slow down your time to market and use the process.