‘Tight’ blood sugar control not always the best course
DEAR DR. K: I have Type 2 diabetes. For years, my doctor emphasized the importance of tight blood sugar control. But I recently read that tight control might not make sense for everyone. Why not?
DEAR READER: Millions of people with diabetes, and their doctors, are asking themselves the same question. It’s a confusing and controversial area. I’ll do my best to put it in context and to explain my own views.
People with Type 2 diabetes have high levels of blood sugar if they don’t take medication that lowers their blood sugar level. Some medicines that successfully lower blood sugar — particularly insulin and sulfonylurea drugs — can be too successful, however: They can drop sugar levels too low. This can produce confused thinking, sleepiness, falls and fractures, loss of consciousness and even death.
So the goal in treating diabetes is to lower high blood sugar levels to normal, but not to below normal. Getting the levels down to normal is called “tight control” of blood sugar.
There are two ways of measuring blood sugar. You can measure the sugar level at the moment that you sample the blood, or you can estimate what the average sugar level has been over the past two to three months using a test called hemoglobin A1c (HbA1c). Most doctors urge their diabetic patients to aim for an HbA1c of 7 percent or less. This is considered tight control.
Aiming for tight blood sugar control makes sense for almost all patients when they are first diagnosed with Type 2 diabetes. In large part, that’s because it often can be achieved with diet and exercise alone. Diet and exercise sometimes can lower blood sugar levels to normal — without the risk of dropping them too low.
Several studies over the past decade have indicated that using medicines to achieve tight control in older ill patients may lead to worse health than shooting for somewhat less than tight control. Tight control may be too much of a good thing. A more modest goal (targeting an HbA1c level between 7 percent and 8.9 percent, for example) might make more sense.
A recent study of 1,288 people age 65 or older found that about two-thirds of people in relatively poor health had achieved an average HbA1c of 7 percent or less over the 10- year study period.
That sounds like good news: Controlling blood sugar helps prevent longterm health problems. But the authors of the study argue that for the sicker patients, that long- term benefit would likely be outweighed by the short-term risks of periodically causing dangerously low blood sugar. Their study did not directly demonstrate such health risks; it was not designed to do so.
If you are taking insulin or sulfonylurea drugs, particularly if you have several other diseases besides diabetes, talk to your doctor. You might benefit from more frequent home blood sugar testing to detect low blood sugar. If the testing reveals that your blood sugar sometimes gets below normal, maybe it’s better to reduce the dose of medicine a bit.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.