Unexplained weight loss: causes and what to do

For your safety, call 911 or go to the emergency room if you also have:

• Vomiting blood or something that looks like coffee grounds
• Black, tarry stools, or blood in your stool
• Fainting, severe dizziness or confusion
• Strong thirst and frequent urination with vomiting that stops you keeping fluids down, fast deep breathing or fruity-smelling breath
• Thoughts of harming yourself: call or text 988 or Línea PAS at 1-800-981-0023

MedlinePlus advises seeing a provider if you have lost more than 10 pounds (4.5 kg) or 5% of your normal body weight over 6 to 12 months or less and you don’t know why, especially if you have other symptoms. For example, for a person who weighs 160 pounds, 5% is 8 pounds.

This is not meant to scare you: many causes are treatable. But it isn’t something to settle by video alone either. You need blood tests and an in-person physical exam.

The table on this page sums up the most common causes. According to MedlinePlus, they fall into these groups:

• Undiagnosed diabetes: weight loss with strong thirst, frequent urination and tiredness. This matters in Puerto Rico: according to a CDC analysis, 14.4% of adults had diagnosed diabetes in 2021, the highest in the US. See high blood sugar.
• Overactive thyroid: with a racing heart, nervousness, feeling hot and more hunger. See hyperthyroidism.
• Poor appetite: from depression, stress or anxiety, or from medicines.
• Digestive problems: diarrhea that won’t go away, parasites, celiac disease or inflammation of the pancreas.
• Long-lasting infections, such as tuberculosis or HIV. See night sweats.
• Chronic diseases of the lungs, heart or nervous system.
• Cancer, sometimes before it causes other symptoms.
• Eating disorders that haven’t been diagnosed.

You see Dr. Diana Nieves Castro, MD, a Puerto Rico–licensed general practice physician with several years of emergency-department experience, in English or Spanish. As MedlinePlus describes, she asks how much weight you have lost and over what time, whether you are eating less, whether you have thirst, diarrhea, vomiting, fever, night sweats or low mood, and which medicines you take.

We evaluate you and help find the cause. We give you a lab order for a lab near you: depending on your symptoms, for example a blood count, blood sugar or hemoglobin A1c, thyroid, liver and kidney tests. We go over the results with you in a follow-up visit. Because you also need a physical exam, we refer you for an in-person evaluation and for the cancer screening tests recommended for your age.

If the cause is diabetes, a thyroid problem or another condition handled in primary care, the doctor explains the plan and, if appropriate, prescribes and we send your prescription to your pharmacy. See primary care.

A doctor visit costs US$79, the same price for every age. Request a visit online 24/7 — we confirm your time by email or text.

MedlinePlus advises getting care if a child or family member loses more weight than is healthy for their age and height. For patients under 21, a parent or legal guardian must be on camera for the whole visit. In older adults, weight loss with poor appetite, mouth or dental problems, or low mood also deserves a prompt evaluation.