I think it depends on the GP, some have more experience than others depending on their patients. However, lots of healthcare people who are not psychiatrists/psychologists are not capable of making the diagnosis. Many do not even believe in mental illness, just like in the rest of society.

So if this is a new physician to you, then I would say be cautious. Don't take the dx for sure just yet. See a psychiatrist.

When you say "mild" mood swings what do you mean? Happy now, sad later? Track your moods more closely with a tracking tool that is actually made to track symptoms of bipolar as well. Not just the smile for good day, frown for bad. You need to have symptoms and not just mood. Racing thoughts, eating and sleeping changes, poor judgement, difficulty concentrating, irrtiability, changes in eating or sleeping patterns, etc. Because bipolar may be called a "mood" disorder, but there is more to it than that.