Suppose your blood sugar is running high on a particular day, and you're not quite sure why. You think back to the morning: did walking rather than driving to work play havoc with your numbers? Or could it have been the cinnamon bun that had your name on it at the local bakery? But you didn't eat the whole thing...or did you?

Remembering precisely what you ate and drank for the past few days can be tricky. Yet, if you want to really find out what's driving your blood sugar up and down, it's essential to see how the numbers are affected by your diet. Many physicians and nutrition experts who treat patients with diabetes ask them to keep a food diary. But many diabetics find this tedious and time consuming, and may not always follow through.

"We ask people to keep a log of both their blood sugar and their food intake," says Caroline Bohl, MS, RD, CDE, of the Naomi Berrie Diabetes Center at Columbia University Medical Center in New York City. "If you see high or low blood sugar numbers, you will know immediately what you did or didn't eat. This can help you make changes."

Not only does keeping a food diary for a few days enable you know what foods are causing your blood sugar to spiral upward, it can help you if you are trying to lose weight and to make certain changes at mealtime, Bohl says. "Keeping a food diary can make you realize the portion sizes you are taking in, and helps you remember that extra cookie you might have grabbed," she says.

Typically, keeping an accurate food diary for just three days can give your doctor or nutritionist enough information to help her plan out any possible adjustments in your medication, and to give advice on any proposed dietary changes.

This can be a difficult undertaking for a couple of reasons. For one thing, it's just plain time consuming. For another, it can feel almost like an invasion of privacy. "It's letting another person into a private part of your life, what you eat and when you eat it," Bohl says. "It makes people look at things they don't want to, and forces them to have some self reflection."

Keeping this practice up makes denial about what you are really eating much harder, says Megan Fendt, RD, CND, CDE, a nutritionist at the Friedman Diabetes Institute at Beth Israel Medical Center in New York City. Yet for anyone serious about getting in good control, it's one of the most basic steps you can take to help yourself.

"A food diary also helps with awareness," Fendt says. "It's easy to forget you ate that bag of chips if it is not written down right in front of you."

The good news is that most experts don't think you need to keep a food diary on a regular basis. If you can maintain an accurate one for just a few days twice a year, your doctors will have a more well-rounded picture of where you stand. And you'll be taking a crucial step in the direction of good health.