Unexplained Weight Loss: Why You Need To See A Doctor

It is common in our society to view weight loss as a positive thing. Being in the ‘healthy weight’ range is often hailed as the pinnacle of good health. Health problems are often blamed on a person’s body weight or any recent weight gain.

Too often, this firmly places the burden of responsibility on the person themselves for becoming unwell, rather than acknowledging the many other determinants of health that can increase someone’s risk of developing illnesses.

These include family history and genetics, social-economic status, physical activity levels, and mental health status, to name just a few. Bodyweight is just one small piece of a very large puzzle when it comes to health.

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There is evidence to show that stigmatization toward people who are of a higher weight can lead to various physical and mental health implications such as low self-esteem, poorer body image, depression, and an increase in binge eating.

Weight stigma aside, losing a significant amount of weight, particularly unintentionally, can actually be damaging to your health. Malnutrition across the globe is a significant issue, and not just in developing countries. This is a fact that often surprises people.

Malnutrition is costly to the economy. It can also increase the risk of illness and a poor quality of life and lead to higher levels of depression and low mood and is worryingly underdiagnosed. In the UK, the charitable organization BAPEN estimates that 3 million people live with the effects of malnutrition, with a staggering 93% of those living in the community.

Hopefully, this brief introduction should be clear that experiencing significant and unplanned weight loss can have significant health implications. It can also be a sign of an underlying medical condition that has gone unchecked. One of the key medical conditions that can cause unexplained and unintentional weight loss is diabetes mellitus (herein referred to as diabetes).

We will provide an overview throughout the article, although the link between diabetes and unexplained weight loss is clear. As such, it is important to be aware of this risk, how to spot any unplanned weight loss, and what you can do about it. 

Read on to find out more about unexplained weight loss, including the link with diabetes. 

What are the possible causes of unexplained weight loss?

As we have already introduced, unexplained and unintentional weight loss can be linked to various health conditions. The most common health-related reasons for unexplained weight loss are (1):

Unintentional weight loss may also occur during or following a period of stress or worry or after experiencing a loved one’s loss. If you think your health may be at risk due to stress or bereavement, it is important you seek support from a medical professional. They will be able to recommend physical or mental health support to help you get through difficult times. 

Some of the less common causes of unintentional or involuntary weight loss are widespread in nature and may include:

  • Dental problems 

  • Side effects from medication, such as taste changes and dry mouth, which may make you eat less

  • Alcohol or drug misuse 

  • Gastrointestinal problems 

  • Bowel problems such as inflammatory bowel disease (IBD) or ulcerative colitis (UC)

  • Conditions that can cause pain and inflammation, such as rheumatoid arthritis 

  • Diseases that affect your kidneys, liver, or heart, such as heart failure 

  • Respiratory conditions, such as Chronic Obstructive Pulmonary Disease (COPD)

  • Diabetes 

A little later on in this article, we will look at more detail about diabetes and sudden weight loss and what to do if you are concerned. 

Firstly, it is important to understand what we mean by ‘unintentional weight loss. You may be asking yourself – what is rapid weight loss, and what is less significant? How do you determine what sudden weight loss is?

Clinically, unplanned weight loss is referred to as being significant when you have lost 5% or more of your body weight in the past 3-6 months. So, if you know you weigh around 70kg (154Ib or around 11 stone) usually, and this goes down to 65kg or less without you trying, then this could be a sign that you need to visit your doctor. 

They will ask you some questions about any other symptoms you may be experiencing and determine if the unplanned weight loss needs to be investigated further with tests.

Key guidance such as ‘NICE guidance for Type 1 diabetes in adults: diagnosis and management, reference rapid weight loss as one of the typical signs seen when diagnosing someone with type 1 diabetes (2). This is relevant regardless of their body mass index (BMI), so it does not matter if they are in the healthy weight range or have a lower or higher body mass index.

The American Diabetes Association also references weight loss as a key symptom for type 1 diabetes. However, they additionally point out that this may occur even though you may be eating more or do not have a decreased appetite (3).  

Diabetes and sudden weight loss

It is fairly well known that weight loss is a common effect of a recent diabetes diagnosis or undiagnosed diabetes. More commonly, this is referred to in relation to type 1 diabetes, although unplanned weight loss can also occur due to undiagnosed and untreated type 2 diabetes. 

When you have diabetes that is undiagnosed or poorly controlled, insufficient insulin levels prevent the body from transporting glucose from the blood into the body’s cells for use as energy.

When the body can’t get sugar into the body’s cells for energy, high blood glucose levels (hyperglycemia) occurs. When someone has persistent hyperglycemia, the body starts to burn fat and muscle for energy, rather than relying on glucose for energy, which is the body’s preferred energy source. This results in a loss of overall body weight. 

Other diabetes symptoms to watch out for 

Additionally to weight loss, there are some other common symptoms of diabetes to watch out for (see below). If you notice any of these symptoms, it is important that you mention them to your doctor, particularly if any of the diabetes risk factors are also relevant to you. Experiencing one single symptom, or more than one, can be a sign of undiagnosed diabetes. The risk factors for diabetes (and prediabetes) include:

  • Having a family history of diabetes

  • Age 

  • Being a certain ethnic background (this differs between the UK and the US), 

  • Or not being in the healthy weight range. 

Having some of the symptoms of diabetes does not mean that you definitely have it, although it is still important to check with your doctor. 

Other symptoms of diabetes to be aware of are (4):

  • Frequent urination or excessive urination (polyuria)

  • Getting urine infections, also sometimes called a yeast infection (genital itching can also be a sign of diabetes)

  • Being more thirsty than usual 

  • Blurred eye site

  • A tingling feeling in your hands and feet 

  • Having wounds, including cuts, that take longer to heal than expected

  • Feeling very tired or fatigued, without knowing why 

However, it is important to note that not everyone who develops type 2 diabetes experiences any symptoms at all. Therefore, if you know that you have some of the risk factors for diabetes, it is important that you visit your doctor for blood tests – an annual check-up is recommended.

For people who develop type 1 diabetes, the symptoms usually develop and show quite quickly, making it far less likely to go unnoticed. 

The symptoms for diabetes occur because there is either no insulin being secreted by the pancreas (type 1 diabetes), there is an insufficient insulin level to control glucose levels in the blood (type 2 diabetes), or the body’s cells fail to respond to the secretion of insulin (insulin resistance). In all of these circumstances, glucose from the food you eat builds up in the blood as it cannot get into the body’s cells to be used as fuel (energy).

Your body will try and reduce these high blood glucose levels by flushing the excess glucose out in the urine. Hence, you will need to go to the toilet more. When you do pass urine, having high sugar levels present poses a risk for bacterial overgrowth – which can cause an infection that then causes thrush (4).

As previously mentioned, the symptoms of type 1 diabetes, which most commonly present in childhood, appear quickly. As a result, they usually prompt a rapid visit to the doctor. Yet, if type 1 diabetes symptoms are ignored, they can lead to significant complications. Type 1 diabetes can lead to a serious condition called diabetic ketoacidosis (DKA) if left untreated. DKA can lead to a diabetic coma, which can be fatal.

Type 1 diabetes is also linked to an increased risk of other conditions, including coeliac disease and problems with your thyroid gland, that can lead to thyroid disease (5). Adults and children with type 1 diabetes should be aware of their risk of developing the coeliac disease and get screened regularly.

If you develop coeliac disease as a result of also having type 1 diabetes, following a gluten-free diet is the only treatment and must be adhered to for life. You can read more about type 1 diabetes and learn about insulin injections as a treatment and how to reduce your risk of complications here

Whilst the symptoms of type 2 diabetes are far more likely to go unnoticed than the symptoms of type 1 diabetes, undiagnosed type 2 diabetes can also lead to serious complications. The longer type 2 diabetes goes unnoticed and untreated, the higher the risk of complications. These include problems with various organs, including your heart and kidneys, and also problems with your eyes, hands, feet, and nerves.

Diabetes can also increase your risk of other chronic diseases such as chronic pancreatitis (a longstanding inflammation of the pancreas that causes significant abdominal pain) and can lead to erectile dysfunction (5). 

With good management of your diabetes, you can significantly reduce your risk of developing complications. It is strongly advised that you engage with your specialist healthcare team, attend regular diabetes checkups, and monitor your own health care to look out for any of the symptoms of diabetes, including unplanned or sudden weight loss.  


At first, you may not view your unplanned or unintentional weight loss as a negative thing. You may not even notice it at first. Yet, along with several other key symptoms, it can be a key sign that you have diabetes. It is always important to look at the whole picture when it comes to your health, and try not to view one sign or symptom in isolation.

Nevertheless, if you have noticed unintentional weight loss, particularly if you have also noticed other symptoms of diabetes or you carry some of the risk factors.

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  1. NHS, Unintentional Weight Loss (2019). (Online). Available: https://www.nhs.uk/conditions/unintentional-weight-loss/ accessed March 2021
  2. National Institute for Health and Care Excellence (NICE). Type 1 diabetes in adults: diagnosis and management.
  3. NICE guidelines. Published: 26 August 2015, accessed March 2021
  4. The American Diabetes Association. (2021). Type 1 Overview: Diabetes Symptoms. (Online). Available: https://www.diabetes.org/diabetes/type-1/symptoms accessed March 2021.
  5. Diabetes UK. (2021). What are the Signs and Symptoms of Diabetes? (Online). Available: https://www.diabetes.org.uk/diabetes-the-basics/diabetes-symptoms accessed March 2021
  6. Diabetes UK. (2021). Diabetes Related Conditions. (Online). Available: https://www.diabetes.org.uk/diabetes-the-basics/related-conditions#pancreatitis accessed March 2021

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