Yes, impaired glucose tolerance is a bad thing. It is sometimes called prediabetes.

In general, the more concentrated the fish oil (higher EPA and DHA ratio) the more processed it is.

Many health websites pick up information from other sites, and pass it along. ONE site that writes a sloppy copy may be repeated ad nauseum on others. This happened with evening primrose oil, which contains GLA. (GLA is also an abbreviation for a totally different substance, a chemical toxic to the brain that causes seizures). Well, somebody did a search and found GLA causes seizures and this was tagged to evening primrose and borage supplements forevermore! It sometimes is best to go to
PubMed directly and do your own search. (that is how I found this confusion with GLA, many years ago). This is one criticism I have with Livestrong site...they paraphrase and use other sites'
comments without being more careful. Sometimes Livestrong is okay and others, not so much.

If anything, I think Omega-3's may LOWER blood glucose, and for those on insulin or oral medications they may need to test more often to see if they are still in normal range when using Omega-3's. I have never seen a paper that they raise blood sugar. Now when people take enormous amounts ---amounts past essential food intake suggestions, THEN being monitored by a doctor is a good idea. I've only met one person taking 13 grams of fish oil for an autoimmune kidney disease who was doing that with his doctor's supervision.