What are the Causes and Treatments of Unexplained Weight Loss?

unexplained weight loss
Medically reviewed by Dr. Ola Tarabzuni


Unexpected weight loss is a significant drop in body weight, regardless of a person’s lack of weight loss intent. Unexpected weight loss may indicate a severe condition, such as diabetes or cancer. The first step in treatment is to determine what is causing the weight loss.

Stressful circumstances like divorce, job loss, or losing a loved one may be the root of it. Malnutrition, a medical condition, or a combination of factors are additional potential causes.

What is Unexplained Weight Loss?

Involuntary or unintended weight loss are other names for unintentional weight loss. This term excludes weight loss brought on by a known sickness or as a predicted side effect of therapy (such as diuretic therapy-induced weight loss in heart failure patients). Clinically significant weight loss is generally understood to decrease more than 5% of one’s average body weight over 6 and 12 months.

What is Considered Unusual Weight Loss?

Unusual weight loss is a term used to describe a significant and unintentional decrease in body weight over a relatively short period, such as a few weeks or months. This type of weight loss is often considered abnormal and may be a sign of an underlying health condition.

The definition of unusual weight loss may vary depending on the individual and their baseline weight. However, a general guideline is that a weight loss of 5% or more of body weight within 6-12 months is considered significant and may require further evaluation.

Remember that not all weight loss is a cause for concern. Many intentionally lose weight through diet and exercise changes, generally considered healthy if done safely and sustainably.

Consult One of Our Doctors Online If you are Facing Unintentional Weight Loss.

What Causes Unexplained Weight Loss?

There can be a variety of underlying medical conditions that cause unexplained weight loss. These can be divided into PHysical causes and Psychological causes

Physical Causes of Unintended Weight loss:


Cancerous tumors can cause weight loss by altering the metabolism or putting pressure on the digestive tract, causing nausea and vomiting.


An overactive thyroid gland can increase the metabolic rate and lead to weight loss.


Uncontrolled diabetes can cause weight loss due to the body’s inability to use glucose for energy.

Chronic obstructive pulmonary disease (COPD) 

It can make breathing difficult, decreasing appetite and weight loss.

Gastrointestinal disorders

Conditions such as inflammatory bowel disease, celiac disease, and gastroesophageal reflux disease can cause weight loss due to malabsorption or increased metabolism.

Chronic infection

Chronic infections, such as tuberculosis or HIV, can lead to weight loss due to the body’s increased metabolic rate.


Chemotherapy drugs or stimulants can cause weight loss as a side effect.

Addison’s disease

It is a rare condition in which the adrenal glands, located on top of the kidneys, do not produce enough hormones, cortisol and aldosterone. This can cause unintended weight loss due to decreased appetite, nausea, and vomiting. 

Parkinson’s disease 

Parkinson’s disease is a chronic neurological disorder that affects movement and coordination. It can also cause unintended weight loss due to decreased appetite, difficulty swallowing, and gastrointestinal problems such as constipation. People with Parkinson’s disease may also have a higher metabolic rate, which can contribute to weight loss. In addition, Parkinson’s disease can cause fatigue and depression, affecting a person’s motivation to eat and maintain a healthy weight.

Parasitic infection 

Parasitic infections such as giardiasis or tapeworm infections can cause unintended weight loss due to decreased appetite, nausea, vomiting, and diarrhea. These infections can also affect the absorption of nutrients, leading to malnutrition and weight loss.


Dysphagia is a condition in which a person has difficulty swallowing. It can cause unintended weight loss due to difficulty eating and drinking and an increased risk of aspiration pneumonia. People with dysphagia may avoid eating certain foods, leading to malnutrition and weight loss.

Dental problems

These include missing teeth or gum disease can cause unintended weight loss due to difficulty eating and chewing food. People with dental issues may avoid certain foods or eat smaller amounts, which can lead to malnutrition and weight loss.

Psychological factors lead

Psychological factors can also contribute to unintended weight loss. Here are some of the psychological causes of unintentional weight loss:


Depression can lead to a loss of appetite and food disinterest, resulting in weight loss. People with depression may also have low energy levels and lack motivation, making them less likely to prepare and eat meals.


People with anxiety may experience symptoms such as nausea, vomiting, and diarrhea, which can contribute to weight loss. They may also have difficulty eating due to the physical symptoms of anxiety or concerns about their weight or body image.

Eating disorders

Eating disorders like anorexia nervosa and bulimia can cause significant weight loss. People with anorexia nervosa restrict their food intake severely, while those with bulimia binge eating followed by purging behaviors such as vomiting or using laxatives.


Chronic stress can affect the body’s cortisol levels, leading to weight loss. Stress can also contribute to unhealthy eating habits, such as skipping meals or overeating, resulting in weight loss or gain.


People with dementia may forget to eat or lose interest in food, leading to unintended weight loss. They may also need help preparing meals and forgetting to eat or skip meals altogether. There is no known cure for dementia, early intervention can slow down its progress allowing the patient to lead a quality life longer.

Substance abuse

Certain substances such as amphetamines, cocaine, and methamphetamine can cause weight loss as a side effect. People who abuse these substances may also have a decreased appetite and neglect proper nutrition.

Medication side effects

Drugs used to treat mental health conditions such as depression, anxiety, and bipolar disorder can cause unintended weight loss as a side effect.

Rapid Weight Loss Can be a Symptom of Serious Illness. Consult One of Our Doctors Now for Evaluation.

How to Diagnose Unexplained Weight Loss

Diagnosing unexplained weight loss includes a detailed history, physical examination, and Investigations depending upon the severity.

Medical history

A thorough medical history is essential to the diagnostic process for unexplained weight loss. Questions to understand better your medical history include any past or current medical conditions, medications you are taking, any recent changes in your lifestyle or eating habits, and any other relevant information.

Here are some examples:

  • Are you experiencing other symptoms besides weight loss, such as fatigue, weakness, or abdominal pain?
  • Any noticeable changes in your appetite or eating habits?
  • Are you experiencing any difficulty swallowing, nausea, or vomiting?
  • Have you had any recent surgeries or medical procedures?
  • Are you taking any medications or supplements? If so, which ones?
  • Have you been diagnosed with any medical conditions, such as diabetes, heart disease, or cancer?
  • Have you experienced any recent trauma or emotional stress?
  • Do you smoke or drink alcohol? If so, how much and how often?
  • Has anyone in your family been diagnosed with any medical conditions?
  • Have you recently traveled to any other countries or regions?

Physical examination 

Your doctor will perform a physical examination to look for signs of illness or disease, such as an enlarged liver or swollen lymph nodes. Some of the specific tests that your healthcare provider may perform during a physical examination to help diagnose the cause of unexplained weight loss

  • General inspection: Inspection of your body, including your skin, hair, and nails, to look for any signs of malnutrition, dehydration, or other physical abnormalities.
  • Vital signs: This includes your blood pressure, heart rate, respiratory rate, and temperature to check for any signs of infection or inflammation.
  • Head and neck examination: To check for any signs of an enlarged thyroid gland, lymph nodes, or other abnormalities.
  • Abdominal examination: Any signs of organ enlargement, such as an enlarged liver, spleen, or other abnormalities.
  • Rectal examination: Your healthcare provider may perform a rectal exam to check for any signs of gastrointestinal bleeding or other abnormalities.
  • Skin examination: Your healthcare provider may examine your skin for signs of rashes, infections, or other skin abnormalities related to an underlying medical condition.
  • Neurological examination: Your healthcare provider may perform a neurological exam to check for any signs of nerve damage or other abnormalities.

Blood tests

These tests help identify any underlying medical conditions causing weight loss, such as anemia, hyperthyroidism, or diabetes. Some essential investigations include

  • Complete blood count ( CBC) with differential
  • Serum Electrolytes
  • Glucose and hemoglobin A1c(HbA1C)
  • Calcium 
  • Renal function( RFT) and urinalysis 
  • Hepatic function (LFT)
  • Thyroid-stimulating hormone( TSH) 
  • Stool Hemoccult 
  • Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) 
  • Human immunodeficiency virus (HIV)
  • Hepatitis C screening
  • Age-appropriate cancer screening

Imaging tests

 X-rays, CT scans, or MRI scans can help identify tumors, infections, or other abnormalities causing weight loss.


In some cases,  endoscopy is recommended to look for abnormalities in your digestive tract that may be causing weight loss.

Mental health evaluation 

Unexplained weight loss can sometimes indicate an underlying mental health condition, such as depression or an eating disorder. Your doctor may refer you to a mental health professional for an evaluation.

Consult One of Our Doctors Online to Get Tested for Significant Weight Loss.

Treatment for Unintentional Weight Loss

Unintentional weight loss can indicate an underlying medical condition or a side effect of certain medications. Therefore, the treatment for unintentional weight loss depends on the underlying cause. Here are some general tips that may help with unintentional weight loss

Consult a doctor

If you are experiencing unintentional weight loss, it is essential to determine the underlying cause. If no reason is identified after investigations and examination, the following things can be tried. 

Eat a balanced diet 

Eating a healthy and balanced diet can help you maintain weight and prevent further weight loss. Eating nutrient-dense whole foods, like vegetables, fruits, lean protein, and whole grains, can help.

Increase calorie intake

If you are losing weight unintentionally, you may need to increase your calorie intake to maintain your weight. This can be done by adding healthy, high-calorie foods like nuts, seeds, and avocados.


Regular exercise can help build muscle mass, which can help prevent further weight loss. It can also help increase your appetite and improve your overall health.

Manage stress

Stress can contribute to unintentional weight loss. Managing stress through meditation, yoga, or counseling, can help you maintain a healthy weight.

Consult One of Our Doctors Online to Treat Drastic Unexplained Loss of Weight.

When to Consult a Doctor?

If you are experiencing unintentional weight loss, Here are some general guidelines for when to see a doctor:

Significant weight loss

If you have lost more than 5% of your body weight in the last six to 12 months without trying to lose weight, it’s a good idea to see a doctor.

Rapid weight loss

For a significant amount of weight loss in a short period (such as 10 pounds or more in a month), it’s essential to see a doctor.

Other symptoms 

If you are experiencing other symptoms along with weight loss, such as fatigue, weakness, or changes in bowel habits, it’s essential to see a doctor.

Chronic medical conditions 

If you have a chronic medical disease, such as cancer, heart disease, or HIV, and are experiencing unintentional weight loss, you must see a doctor.


If you take medicines that may cause weight loss as a side effect, you must talk to a doctor about potential alternatives or ways to manage the side effects.

FAQs about Unexplained Weight Loss Answered by Your Doctors Online Team

What cancers cause rapid weight loss?

Several types of cancer can cause rapid weight loss, often a sign of advanced disease. These cancers include pancreatic, stomach, esophageal, lung, and some types of leukemia. Rapid weight loss can occur because cancer cells use a lot of energy and nutrients from the body, leading to muscle wasting and decreased appetite. Additionally, some cancers can affect the digestive system, making it difficult for the body to absorb nutrients properly.

Why am I losing weight despite eating more?

There are multiple reasons why you may be losing weight despite eating more. One possibility is that you are experiencing increased physical activity, burning more calories, and leading to weight loss. Another possibility is that you have increased your muscle mass, which is denser than fat and can lead to weight loss even if you consume more calories. However, if you are experiencing unexplained weight loss despite eating more, it may indicate an underlying health condition such as an overactive thyroid, celiac disease, or inflammatory bowel disease. Additionally, certain medications, such as those used to treat diabetes or depression, can cause weight loss as a side effect. You are advised to consult a doctor immediately in case of unintentional weight loss. 

How much weight loss is concerning?

The amount of weight loss that is considered concerning varies depending on the individual and their overall health. Generally, losing more than 5% of your body weight within six to 12 months without intending to lose weight may be a cause for concern. If you are losing weight drastically, which is losing 10 pounds or more within a month, it can also be concerning and should be evaluated. Additionally, suppose you are experiencing other symptoms such as fatigue, weakness, or changes in bowel habits. In that case, it is advised to consult a health professional to determine the underlying cause of your weight loss.

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