Alison, I had a situation a few months ago when lunching with some of my OH's extended family, whereby the lady sitting next to me pretty much described the warning signs to me, and rounded off saying she'd probably need a nap after lunch. The young lady is in her mid-40s, so all grown up, with a great career, madly busy family life and all the usual stuff. She is a very determined person, and almost as stubborn as I am (nobody out-ranks me in the stubborn department!), so telling her what to do wouldn't be met with a positive response. During the afternoon, I had a bit of think about how to tackle some of the things I wanted to say, and came up with this strategy.
I told her that a few years ago I'd had a few of the symptoms she was experiencing (actually that was an untruth, but heh,...... I'll live with it) and realised that my symptoms ebbed and flowed around my eating, so I started experimenting with my diet. As she had historically found she could induce or prevent her migraines by eating, or declining certain foods, I knew that might prick her interest. I explained that it fairly quickly became clear that when I had a carb-tastic meal - like a sandwich, with a cake afterwards or a pasta salad, just as easy but quite extreme examples, I felt a bit weary afterwards. Having got there, I decided to knock those things on the head for a week and see how I felt. I told her I based my "exclusion" eating on the Atkins programme, to make it easily Google/research-able. I didn't link it to diabetes. In my experience, people, generally, are far more open too discuss food intolerances than anything you give a condition/disease name to.
Anyway, fast forward a month or so and she told me she had tried the Atkins and was astonished by how she felt within a week, after a few days of carb withdrawal. I may possibly have been somewhat minxy in suggesting that carb-flu was probably a good sign that she was getting rid of an overload on her system. 😳 She had also lost weight, which she has always struggled to do.
At the end of our subsequent chat, I suggested she should have a chat with her Doc and maybe have some bloods done, as she works rotational shifts and suggested she look up Vitamin D and shift working.
She's had the usual bloods done, and although not diabetic, she is perilously close to pre-diabetes, and lacking Vitamin D, so her Doc has given her Vit D and wants to retest in 3 months. She's sticking with an Atkins-ish diet as she's now finding it quite easy.
Who knows what the future holds for her, but trimming up a bit and sorting her Vit D can't have harmed her anyway.
Of course, I may never get to heaven, but I just knew giving her an easy way to explore was more likely to succeed that have her think I was being a know-it-all.
As my OH has said to me many times,............... "You know, you can't cure the world." That's usually when I'm watching folks on a reckless life path, with complete disregard how their own well-being.
It's tough to watch a car crash unfold before the eyes.
Of course, it's the possible consequences of that test that are frightening and I do understand that feeling of just not wanting to know, unless it's good news (feel that way about the problems with my eyes). Not a great deal you can do beyond what you have already done, horses to water and all that 
