In the IHIS "Weight" variable, what do 997, 998, and 999 code for?

I am using IHIS Person data for years 1999-2001. Most obvservations for “Weight” fall in the reasonable range of 100-285, but about 600-800 observations each year are either 997, 998, or 999. I assume these are codes for something, but I was hoping to figure out what they code for. Is one of them an indicator for the fact that this person’s weight was greater than 285, since 285 seems to be the largest weight assigned to any person?

The “Height” variable has information on codes in the description, but this information is absent for the “Weight” variable.

Thanks in advance for the help.

For the WEIGHT, a code of 997 represents a response of “Unknown – Refused”, 998 represents “Unknown – not ascertained”, and 999 represents “Unknown – don’t know.” These definitions are provided in the Command Files that are generated alongside your data extract. I apologize for the confusion and I hope this helps.