Measuring waistline
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Unexplained Weight Loss

If you lose more than 5% of your weight in 6 to 12 months, tell your doctor, especially if you’re an older adult. That would be about 8 pounds if you weigh 150, or 10 pounds if you weigh 200. Sudden weight loss without a reason can be a sign of a health problem.

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Thyroid exam
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If your thyroid gland makes too much thyroid hormone, it revs up your metabolism so you burn more calories and lose weight. You also may have more bowel movements and a racing heartbeat, and you may feel anxious. Your doctor can help you manage it with medicine. They may also talk to you about surgery to take out all or part of your thyroid.

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Insulin is a hormone your body makes to turn blood sugar into energy. If you have diabetes, you either can’t make insulin or can’t use it the way you need to. When your cells run out of fuel, your body thinks it’s starving and starts burning fat and muscle. This makes you lose weight. You may also be thirsty, tired, hungry, or pee more than usual. Talk to your doctor right away if you notice these symptoms. If you have diabetes, they can help figure out a treatment plan that’s right for you.

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wheat field
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Celiac Disease

If you have this, your body reacts to gluten, a protein found in wheat and other grains. When you eat it, your immune system -- which helps you fight off bacteria and other germs -- attacks your small intestine by mistake. That can make it hard for your body to take in nutrients, and that can lead to weight loss. You also may have headaches, itchy skin, sores in your mouth, and joint pain. Only a doctor can tell you for sure if you have it. If you do, you’ll need to follow a special diet to stop the symptoms.

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Prescription meds
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Drugs used to treat certain health conditions may ramp up your metabolism so you burn more calories or make you less hungry. These include:

  • Stimulants
  • Chemotherapy drugs
  • Antidepressants
  • Drugs for type 2 diabetes

Talk to your doctor if you lose your appetite or start losing weight on a new medication. 

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Therapy session
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It’s normal to drop a few pounds after something like losing a job, a divorce, or the death of a loved one. You should return to your regular weight once you have time to grieve the loss or get used to the change. You may need help from family and friends, group therapy, or a professional counselor. Talk to your doctor if you keep losing weight.

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Knee pain
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This is when your immune system turns on your body and attacks your tissues and organs. You may lose weight because it can irritate your digestive system and make it hard for your body to take in nutrients from food. You may be very tired, and your joints may hurt or be stiff. Many people also get a butterfly-shaped rash on their faces. Your doctor can help you ease these symptoms with medicine and changes in your diet and lifestyle.

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Addison’s Disease

With this condition, your adrenal glands don’t make enough of certain hormones, especially one called cortisol. It can cause stomach issues like nausea, vomiting, belly pain, and, in some cases, diarrhea. These things can make you lose your appetite and eventually lose weight. Your doctor can help you manage your symptoms and give you medicine to replace the hormones.

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cancer cells
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These harmful cells may use more of your energy, or they might make chemicals that change the way you digest food. Your immune system often has to work harder, too. That tires you out and makes your body burn more calories, which can lead to weight loss.

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This disease damages tiny air sacs in your lungs. It’s often caused by smoking. It makes it hard to breathe and makes you cough up a thick fluid called mucus. Your body needs more calories to get enough oxygen into each breath. You may also get tired easily and lose your appetite. These things all can lead to weight loss. 

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chest pain
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Heart Failure

If your heart can’t pump blood and oxygen to the rest of your body like it should, your digestive system may not get enough blood to do its job well. This can make you feel full even when you haven’t eaten and may make you sick to your stomach. Eventually, your body might not be able to get rid of fluid like it should, and it can build up in your intestines and keep you from taking in nutrients. Your doctor may recommend that you cut down on salt and give you medicines called diuretics that help you clear out the fluid.

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Two men dining
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This weakens your ability to think along with your basic memory and social skills. In later stages, you may lose a lot of weight because you forget to eat or find it harder to chew or swallow. Chronic infections, special diets, and drugs used to treat dementia can make it worse.

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Sources | Medically Reviewed on 07/11/2019 Reviewed by Michael Dansinger, MD on July 11, 2019


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  12. Thinkstock Photos “What Is Aids Wasting?”

American Cancer Society: “Signs and Symptoms of Cancer.”

American Heart Association: “Warning Signs of Heart Failure.”

Cleveland Clinic: “Unexplained Weight Loss? Why You Need to See a Doctor.”

CDC: “Smoking and COPD.”

Harvard Health Publications: “Do you have an overactive thyroid?”

Health24: “Meds that cause extreme weight loss.”

Lung Institute: “6 Tips for Gaining Weight with COPD.”

Mayo Clinic: “Heart Failure,” “Dementia,” “Addison's disease,” “Lupus,” “Celiac disease,” “Hyperthyroidism (overactive thyroid),” “Unexplained weight loss.”

Nemours Foundation: “Eating Disorders.”

NHS: “Unintentional weight loss.”

National Organization for Rare Disorders: “Addison’s Disease.”

UpToDate: “Lupus.”

U.S. Department of Veterans Affairs: “How is HIV Treated?”

Western Sydney University: “Understanding weight loss in

advanced dementia.”

Reviewed by Michael Dansinger, MD on July 11, 2019

This tool does not provide medical advice. See additional information.

THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the WebMD Site. If you think you may have a medical emergency, immediately call your doctor or dial 911.