I worry a lot about Mark, Liz and Julia. Mark was my flatmate in London in 1975, and we’ve kept in close touch ever since. Liz and Julia are my sisters-in-law. They all have diabetes. I already lost a dear friend to diabetes last year. I don’t want to lose another one.  All three are very diligent about keeping their sugar levels under control. But it’s a huge hassle — and it’s expensive. It costs $25…