When you jumped on the scale this morning, your weight was five pounds less than it was a week ago. You haven’t cut back on calories or ramped up on exercise. Should you be concerned?

Probably not. It’s common for a person’s weight to fluctuate a bit. In fact, it can change up to five or six pounds in a single day. But if you haven’t significantly adjusted your diet or exercise routine, yet your weight is trending downward as the months go by, it could be a sign of a medical condition.

Below, we discuss possible causes for unexplained weight loss and what to do next.

What it means to have unintentional or unexplained weight loss

Unexplained weight loss is when you lose a significant amount of weight in a short amount of time (6-12 months) and there doesn’t seem to be a reason for it.

For example, you haven’t started eating more protein and less carbs, or stopped snacking between meals. You also haven’t changed your workout routine, started any active hobbies like gardening or a recreational sport, or switched to a job where you need to move more.

People most likely to experience unexplained or rapid weight loss

Anyone can experience unexplained or sudden weight loss, but it can be more common in certain groups of people:

Unexplained weight loss in younger vs. older adults

People of all ages can experience sudden weight loss. But it’s most common in older adults who are over 65 years old because they are more likely to have health conditions that cause unintentional weight loss.

Sudden weight loss in men vs. women

People of all genders can experience unintentional weight loss. But some medical conditions that cause sudden weight loss are more common in different genders. For example, men are more likely to have heart disease, diabetes and Parkinson’s disease. And women are more likely to have thyroid problems, mental health concerns and digestive problems. But everyone is different, which is why it’s important to talk to a doctor about your unintentional weight loss.

When to be concerned about unexplained weight loss

So, what amount of unexplained weight loss is concerning? It depends a little on your starting weight.

If your normal weight is over 200 pounds, a loss of 10 pounds or more may be concerning. If your normal weight is less than 200 pounds, it can be concerning to lose more than 5% of your body weight. That means if you typically weigh 140 pounds, you’d want to talk to your doctor if you’ve lost seven or more pounds.

Unexplained weight loss can be especially concerning for people who are more likely to get sick. So if you have a weakened immune system, have been told you are immunocompromised, are over 65 years old or have other medical conditions, it’s a good idea to talk to your doctor about any weight loss – even if it’s just a few pounds.

Causes of sudden or unintentional weight loss

While there are many possible causes of unexpected weight loss, it’s usually due to an underlying medical condition. In fact, research shows that an underlying medical condition is the cause of unexpected weight loss 72% of the time. However, there are also several lifestyle factors that can contribute to unintentional weight loss.

Medications and addictive substances related to unexplained weight loss

Use of prescription medications, recreational drugs, tobacco and alcohol can affect the numbers you see on the scale. Here’s how:

Medication side effects

Sometimes unintentional weight loss is not a sign of a medical condition, but a side effect of medication your doctor prescribed to treat that medical condition. So if you notice that your weight is down after starting a new prescription, check the label for side effects such as unintended weight loss, nausea, vomiting, difficulty swallowing and loss of appetite.

If your weight loss is related to medications, a doctor will be able to help you figure out what needs to be done – whether it’s diet changes or a different medication.

Substance use problems

People who overuse addictive products like tobacco, alcohol and recreational drugs may be more likely to experience unintentional weight loss. Some addictive substances suppress appetite or make eating unappealing. Having a substance use disorder also makes it harder to maintain a balanced diet.

Substance use problems are a risk factor for many different medical conditions. If you need help, make a primary care appointment. They’ll listen without judgment and help identify a treatment plan.

Blood imbalances that can cause unexplained weight loss

Blood is important because it carries nutrients, water and oxygen to every cell in your body – and helps fight off infection and disease. But if the nutrients in your blood become unbalanced, it can affect how your body works, causing symptoms such as unexplained weight loss.

High blood sugar in people with diabetes

Your body gets energy from food in a form of sugar called glucose. Insulin, a type of hormone made by the pancreas, helps your cells use glucose for energy. If you have diabetes, your body doesn’t produce enough insulin or is unable to efficiently use insulin. If your body is unable to get the glucose to your cells, it stays in your blood causing hyperglycemia or high blood sugar.

If your cells are unable to use glucose as an energy source, your body may burn fat and muscle instead. This can cause unexplained weight loss in people with diabetes. Other symptoms include fatigue, vision changes, extreme hunger, mood changes, nausea, vomiting and trouble breathing.

High blood calcium

If you have hypercalcemia, it means that you have too much calcium in your blood. High blood calcium is usually caused by overactive parathyroid glands in your neck, but it can also be caused by medications, taking too much of calcium and vitamin D supplements, and other medical supplements.

Hypercalcemia can cause digestive problems and weakened bones, leading to unexpected weight loss. Other symptoms include abdominal and muscle pain, mood changes and kidney disorders.

Low blood sodium

If the sodium levels in your blood are too low, it’s called hyponatremia. This can happen if you drink a lot of water, since it can dilute the sodium levels in your blood. But hyponatremia can also be caused by diarrhea, dehydration and drinking too many alcoholic beverages.

If you have a mild case of hyponatremia, you won’t have any symptoms. But if your sodium levels are very low, you may have symptoms such as fatigue, nausea, confusion, muscle spasms, low blood pressure and dark urine.

Glandular conditions that can cause unexplained weight loss

Your glands produce substances that support your body’s growth, development, metabolism and other functions. When your glands aren’t working correctly, it can lead to unexpected weight loss.

Overactive thyroid gland

Your thyroid gland is located at the front of your neck. It produces the thyroid hormone which helps control your metabolism, heartbeat, temperature, mood and more. If your thyroid gland makes too much of this hormone, it can cause your metabolism to speed up, rapid weight loss, rapid heartbeat and mood shifts.

Adrenal insufficiency

Adrenal insufficiency, also called Addison’s disease, is when your adrenal glands don’t produce enough of certain hormones, including the one responsible for adrenaline. If the glands don’t produce enough cortisol and aldosterone, you may experience unexpected weight loss, changes in skin tone, fatigue and dizziness.

Mental health conditions that may cause unexpected weight loss

Mental health affects people in different ways. Some people with mental health disorders may experience unexplained weight loss, while others may experience unintended weight gain. The following are some examples of how mental health condition may lead to unexpected weight loss:


Depression weight loss usually comes from eating less. This can happen if you don’t have the energy to prepare food or you no longer find joy in eating. But it can also be because you don’t have an appetite – depression can affect the hormones that tell your body when you’re hungry and when you’re full.


Anxiety can cause unintentional weight loss because you may eat less and move more. For example, you may skip meals because you’re too worried to eat. You may also pace, fidget or bounce your leg while sitting.

Chronic stress

If you’re always stressed out, you might miss meals or make poor food choices. Stress can also cause physical symptoms like fatigue and indigestion, that make food hard to swallow.

Eating disorders

If a friend or family member has symptoms of an eating disorder, it may look like they have unexplained weight loss. It can be hard to know what to do if you think someone has an eating disorder, especially if a person is unwilling to talk about it. Some of the most important things you can do are to let them know you support them and encourage them to get the help they need.

Neurological disorders that can cause unexplained weight loss

There are a wide range of conditions that can affect your brain and neurons. Neurological disorders can cause unintentional weight loss because of changes to behaviors, metabolism and appetite.


Dementia is the term used for a group of symptoms that affect memory, thinking and personality. The symptoms of dementia are caused by changes in the brain.

If a person with dementia has unexplained weight loss, it’s usually because they aren’t eating enough food. It could be that their food preferences have changed or that food is difficult to swallow. It’s also possible that the person with dementia can’t recognize food.

Parkinson’s disease

Parkinson’s disease is a brain illness that impacts your movements. Signs of Parkinson’s disease include body tremors, stiff muscles and limbs, slow movements, balance problems and speech changes.

Weight loss with Parkinson’s is usually from a combination of decreased appetite, your body working harder and changes in digestion that make it more difficult to get nutrients from your food.

Previous stroke

If you’re recovering from a stroke, it’s possible that you may have unexplained weight loss. This can happen if you’re having difficulty eating or digesting food, or because of muscle loss.

Digestive conditions that can cause unexpected weight loss

Everyone gets an upset stomach now and then. But some digestive conditions can have severe symptoms, especially if you don’t have the appropriate treatment.

Inflammatory bowel disease

Inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis, can affect your ability to eat and digest food. You may experience unintentional weight loss because of chronic diarrhea, vomiting or you’re not getting the nutrients you need from your food. It could also be that nausea, indigestion and other symptoms may make eating unappealing.

Celiac disease

If you have celiac disease, it means your body can’t process gluten, a protein that’s found in wheat, barley and rye. Eating foods containing gluten causes an immune response in your small intestines, making it so your body can’t absorb all the nutrients from the food. This can result in unexplained weight loss, diarrhea and fatigue, and lead to serious complications.

Peptic ulcer

A peptic ulcer is an open sore that can develop in the lining of your stomach or upper intestines. These sores are caused by a chemical imbalance in your digestive fluids. Imbalanced stomach fluids can be caused by frequent use of nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen. It’s also possible that a bacteria called Helicobacter pylori can increase the acid in your stomach and cause ulcers. There are rarer causes of increased acid levels as well.

If you have a peptic ulcer, you may be unable to absorb nutrients from food, leading to unexplained weight loss. Other signs of peptic ulcers include burning stomach pain, vomiting and bloody poop.


Your pancreas produces enzymes that help with digestion. If you have pancreatitis, or an inflamed pancreas, your body won’t be able to properly break down food. This can lead to unintended weight loss, nausea, vomiting, diarrhea and oily, fatty or floating stools.

Weakened organs as a cause of unexplained weight loss

Conditions that affect your lungs, heart and other organs can cause unintentional weight loss in a variety of ways.

Protein buildup in organs and tissues

Amyloidosis is a condition where amyloid, an abnormal protein, builds up in your tissues or organs. This protein buildup can damage your tissues and organs. If you have amyloidosis, you may lose your appetite. If amyloid builds up in your digestive system, it can affect digestion and your ability to absorb nutrients from your food.

Heart failure

If you have heart failure and your heart is weakened, your body needs to work harder to pump blood throughout your body. Because of this, you may lose fat or muscle.

People with heart failure may not always notice a weight change since another side effect of congestive heart failure is water retention. Other signs of heart failure include a thin face, and bloated legs and stomach.

Chronic obstructive pulmonary disease (COPD)

If you have COPD or emphysema, it means that your lung tissue is blocked, and it takes a lot of effort to breathe. Since much of your body’s energy is focused on breathing, the rest of the body may not get enough oxygen.

Weight loss from COPD usually happens in the later stages of the disease. This can happen because you’re too tired to eat, you don’t have an appetite or swallowing is uncomfortable.

Serious infections that can cause sudden weight loss

It’s not uncommon to drop a few pounds when you’re sick – the weight usually comes back once you’re feeling better. But if you have a serious or ongoing infection, it can cause increased and lasting weight loss. Infections that can cause unexplained weight loss include:

Parasitic infections

If you started losing weight after an international vacation, you may have gotten an intestinal parasite from something you ate or drank. Parasitic infections can cause abdominal pain, diarrhea, nausea and vomiting, as well as more serious symptoms. But the good news is that they usually go away pretty quickly with treatment.


The human immunodeficiency virus (HIV) damages your immune system, affecting your body’s ability to fight off infections and disease. HIV is spread through sexual intercourse, by coming in contact with infected blood, or sharing injection needles.

Over time, and without treatment, HIV can become acquired immunodeficiency syndrome (AIDS). But newer medications are very effective at controlling HIV symptoms and stopping the progression to AIDS.

In addition to weight loss, other symptoms of HIV and AIDS can include diarrhea, fever, fatigue and swollen lymph nodes.


Tuberculosis (TB) is a potentially serious disease that’s spread through the air through coughs and sneezes. TB can affect almost every part of your body but most commonly is found in your lungs. TB is a relatively rare condition and it’s more common in people who have weakened immune systems, use IV drugs or spend time around people who have TB.

Symptoms of TB can include fever, unexplained weight loss, night sweats, persistent cough, chest pain and coughing up blood.

Cancers that can cause rapid weight loss

If you’re experiencing unexpected weight loss, cancer is not the most likely cause. But it’s true that unexpected weight loss can be one of the first visible signs of cancer. In fact, 40% of people have unexplained weight loss when first diagnosed with cancer, according to the American Society of Clinical Oncology.

Cancer is when abnormal cells grow uncontrollably, or multiply and spread to other parts of the body.

While all cancers can cause unexpected weight loss, clinical studies show that weight loss was more often linked to the following types of cancers: prostate, colorectal, lung, throat, pancreatic, ovarian, kidney, skin, bile duct and non-Hodgkin's lymphoma, which is a certain type of blood cancer.

People with cancer may lose weight because of increased metabolism, muscle loss, fatigue and reduced appetite.

Getting a diagnosis for unintentional weight loss

To help determine the cause of your unexpected weight loss, your doctor will ask you about your symptoms, physical and mental health, and medications. They’ll also review the results of any cancer screenings you’ve done in the past. Depending on what your doctor discovers, they may recommend specific tests based on the potential cause of your unexplained weight loss. They may also refer you to a specialist.

Tests done for unexplained weight loss

Blood tests are commonly used to diagnose the cause of unexplained weight loss. Still, it’s possible to have blood tests that are normal but still be losing weight. That’s because some causes of unexplained weight loss can’t be found through blood work, including neurological disorders, mental health conditions and early-stage cancer.

Other tests your doctor may recommend include imaging scans (like X-rays) and mental health screenings. And to help catch cancer early, when it’s most treatable, you’ll want to stay current on the preventive cancer screenings covered by insurance.

When to see a doctor about unexplained weight loss

If you’re experiencing unexplained weight loss, you should make a doctor’s appointment as soon as you can. If your weight loss is being caused by a medical condition, it’s always better to catch it early. That’s because the sooner you find out what’s causing your weight loss, the sooner you can take steps to address it.

Your doctor may also refer you to a specialist if they think it’s necessary.