Should I be concerned?

My son is 5 years old and has been experiencing very frequent urination, a lot of times, every hour or two.  He has also lost about 3 pounds in the last 2 months.  He was tested in the drs. office in August and they said his glucose levels were fine.  However, I was over my parents house yesterday and tested him 15 minutes or so after he had eaten and he was 174.  My mother is Type 1, and on an insulin pump although she didn't develop it until she was in her late 30's. Should I be concerned about his blood level??