I Have a Cat [Cats]

I have a 17 year old cat...Been with me through so much. He can be a little antagonizing yet he's lovable.
I worry about him. He appears to feel lighter when I lift him...He seems to be eating OK..Just I have had to feed him soft can food more now..
He still can jump on the dresser..And walk around ok...
I am thinking about getting some blood test done. Hate when my dear friend ages...