| From a guy's perspective...
If it turns out he does have diabetes, then be aware of it, and then pretty much ignore it without putting him on the spot about it. Don't be too sympathetic, don't treat it like it's a major disaster. Just shrug your shoulders and carry on exactly how you have been before.
This might sound a bit hollow or harsh, but in my experience women have a tendency to care too much about all sorts of things. It's an amazing gift and something that should be treasured. But most guys don't like a fuss being made - they don't actually like sympathy. We do appreciate understanding though, so yeah, read up on diabetes if he does have it, but don't push him too hard. Don't become his second doctor because that's his job and if you push him too hard, he might push himself away, and you don't want that.
The fact that he actually listen to your concerns and did something proactive is a sign that he trusts you a lot - 90% of people who get told by someone else that they might have symptoms of diabetes tend to just ignore it, so kudos to you and to him for being sensible. Keep up whatever it is you've been doing so far because it looks like you're on the right track.  | 
