What is prediabetes? For that matter, what is diabetes?
Both these conditions are usually diagnosed on the basis of your fasting blood glucose (BG) levels. Current standards are that a fasting BG level of 126 mg/dL or more constitutes diabetes, and anything between 100 and 125 mg/dL constitutes prediabetes.
But not long ago, you had to have a fasting BG level over 140 to be diagnosed with diabetes and a fasting BG level over 110 to be diagnosed with prediabetes. It's possible they'll continue to reduce the cutoff points even more sometime in the future.
That's the confusing thing about prediabetes, the idea of a cutoff point. Fasting BG levels can vary a lot. One day you might have a fasting level of 95, and the next it might be 105, and the next down to 99. Does that mean you are nondiabetic on Tuesday, prediabetic on Wednesday, and nondiabetic on Thursday?
Of course not. The fasting BG level is just a crude estimation of how well you're able to control your BG levels, and someone, usually a committee of experts in the disease, comes up with a cutoff point to allow physicians to decide when to diagnose someone with prediabetes or diabetes.
It's not like having a broken leg, when either your leg is broken or it isn't. Diabetes involves a continuum. When you're young, your fasting BG levels might be in the 70s. Fasting BG levels in the 80s are considered pretty normal. And as you age, your control of your BG levels usually gets worse, so even if you're not prediabetic and you had lower BG levels when you were young, you might regularly have fasting levels in the 90s as you age.
Normal BG levels are discussed here, and there's a link to a graph showing BG levels in nondiabetics. You can see how much they vary.
So is the idea of prediabetes useless? Should you just ignore a diagnosis?
Absolutely not! What prediabetes really means is that you're losing control of your BG levels, and if you don't do anything to control the situation now, there's a very good chance you'll progress to full-blown diabetes.
It's analogous to putting on weight. You may start off with normal weight, and then in middle age you put on a few pounds. You're still not overweight, but if the trend continues, you'll be overweight and eventually obese. It makes sense to try to control the situation as soon as possible, before you're really fat, or before you're diabetic.
So how can you control your BG levels? The two primary ways are controlling your weight and controlling what you eat. If you're already overweight, you already know how difficult it is to lose weight. But if you can manage to do that, your prediabetic BG levels may revert to normal. Once you've reached real diabetic BG levels, the probability of reverting to normal is much lower.
Controlling what you eat is equally important. Try to avoid "high-glycemic" foods, those that raise your BG levels really fast, meaning sugar, white flour, rice, and even starchy vegetables like potatoes and bananas. Some people would urge anyone with a diabetic tendency to go on a low-carb diet, but this is sometimes difficult to do unless you're supermotivated.