By now, Ora Larson recognizes what’s happening. “It feels like you’re shaking inside,” she said. “I’m speeded up. I’m anxious.” If someone asks whether she would like a salad for lunch, she doesn’t know how to respond.

She has had several such episodes this year, and they seem to be coming more frequently.

“She stares and gets a gray color and then she gets confused,” her daughter, Susan Larson, 61, said. “It’s really scary.”

Hypoglycemia occurs when levels of blood sugar, or glucose, fall too low; a reading below 70 milligrams per deciliter is an accepted definition. It can afflict anyone using glucose-lowering medications to control the condition.

But it occurs more frequently at advanced ages. “If you’ve been a diabetic for years, it’s likely you’ve experienced an episode,” said Dr. Sei Lee, a geriatrician at the University of California, San Francisco, who researches diabetes in older adults.

The elder Ms. Larson, 85, has had Type 2 diabetes for decades. Now her endocrinologist and her primary care doctor worry that hypoglycemia may cause falls, broken bones, heart arrhythmias and cognitive damage.

Both have advised her to let her hemoglobin A1c, a measure of average blood glucose over several months, rise past 7 percent. “They say, ‘Don’t worry too much about the highs — we want to prevent the lows,’” the younger Ms. Larson said.