Dear Dr. Roach: I am a 75-year-old woman with a weight problem. My weight used to fluctuate from 130 pounds to 160 pounds. Then I started to notice that I was losing weight slowly but surely on my regular diet. My doctor did not have an answer. Soon I got down to 95 pounds. My family urges me to eat more than I feel comfortable with. I weigh 104 pounds today.

Do you have any idea what could be causing this dramatic weight loss? I still struggle with keeping my weight up to 105 pounds! My height is 5 feet, 4 inches, and I really am quite “bony.” Thank you for any help you can give me.

— A.S.

Answer: When we see dramatic weight loss like yours (greater than 5% to 10% is generally considered important, and yours is greater than 30%), we think about a few important categories. Of course, some of these aren’t appropriate for you, but I want to give an idea of what goes through a doctor’s head when we see a person with this much weight loss:

Unfortunately, cancer tends to leap to our minds, even though it’s not the most common cause. A full-body scan is not usually indicated or helpful. Instead, a careful and focused history and physical exam will often give clues as to whether cancer is likely.

In addition, doctors want to make sure that the person is up-to-date with their age-appropriate screenings, which include breast and colon cancer screenings in a 75-year-old woman. In a person with a history of smoking, I always consider lung cancer and will usually order at least an X-ray.

A condition that is commonly forgotten when thinking about weight loss is the inability to absorb food properly, and celiac disease is the most common disease to cause this. Diarrhea is common but not always present with this condition. People can lose calories through their kidney as well, and diabetes is by far the most likely cause, although there are rare other causes.

Excess urination is universal in uncontrolled diabetes but can be minimized by the patient. Endocrine disorders, especially hyperthyroidism, often cause weight loss. Mental health issues, especially depression, are very commonly associated with weight loss. Anorexia nervosa is uncommon but not impossible in older adults. Any serious disease — heart, lung, liver and others — can also cause serious weight loss. Some medications can cause unexpected weight loss as well.

Chronic infections are also important causes of unexplained weight loss. Tuberculosis, HIV and viral hepatitis are the most common, but there are many uncommon and rare infections.

As adults get older, some degree of weight loss is expected. It is the degree and speed of weight loss that needs to be considered to decide whether this is a serious medical issue. Since it sounds like your weight loss has come on quickly, this is more concerning but a bit less so since it seems like it has stabilized. Still, were you my patient, I’d recommend a more thorough evaluation than it sounds like you’ve had.

I learned a valuable lesson after I made a home visit to give a patient a thorough medical evaluation about her continued weight loss. I found that she had inadequate food at home and was too embarrassed to tell me.

CORRECTION: In a recent column that ran on April 4, we mistakenly referred to an echocardiogram as an electrocardiogram (EKG) in two instances. While the patient’s watch had an EKG function, he was due to have an echocardiogram at the cardiologist.

Contact Dr. Roach at ToYourGoodHealth@med.cornell.edu.