What is the difference between lactose intolerance and irritable bowel syndrome (IBS)?

Karolina Baker, Alphabiolabs

By Karolina Baker, Health Testing Specialist at AlphaBiolabs
Last reviewed: 16/12/2022

In this article, we look at the difference between lactose intolerance and irritable bowel syndrome (IBS), the signs and symptoms of each condition, and why it is important not to confuse the two.
Table of contents
  • What is lactose intolerance?
  • What are the symptoms of lactose intolerance?
  • What is irritable bowel syndrome (IBS)?
  • What are the symptoms of irritable bowel syndrome (IBS)?
  • What is the difference between lactose intolerance and IBS?
  • Who is most at risk of lactose intolerance?
  • Who is most at risk of IBS?
  • How is lactose intolerance diagnosed?
  • How is IBS diagnosed?
  • How is lactose intolerance treated?
  • How is IBS treated?
  • Can you have IBS and lactose intolerance at the same time?

What is lactose intolerance?

Lactose intolerance is a common digestive issue where the body fails to produce enough of the lactase enzyme, which is required to break down lactose in the body.

Lactose is a type of sugar composed of galactose and glucose and is mainly found in milk and dairy products. Most mammals are born with the ability to digest lactose, because it is the sugar found in mammalian breast milk.

However, for people who are lactose intolerant, the body produces little to no lactase, meaning that the sugar remains intact and is fermented by bacteria in the colon.

This fermentation process causes unpleasant symptoms such as bloating, flatulence, nausea, vomiting or diarrhoea.

There is no cure for lactose intolerance, but the symptoms can be managed by adhering to a lactose-free diet.

There are four different types of lactose intolerance: primary lactose intolerance – the kind we test for at AlphaBiolabs – secondary lactose intolerance, developmental lactose intolerance and congenital lactose intolerance.

You can learn more about lactose intolerance here.

What are the symptoms of lactose intolerance?

Some of the most common symptoms of lactose intolerance include:

  • Flatulence
  • Bloating
  • Stomach pain and cramping
  • Stomach rumbling
  • Nausea
  • Vomiting
  • Diarrhoea (sometimes followed by constipation)
If you think you may have lactose intolerance, it is important to speak to your GP who will be able to provide guidance on testing and diagnosis.

What is irritable bowel syndrome (IBS)?

Irritable bowel syndrome (IBS) is a common digestive issue that affects the stomach and intestines (gastrointestinal tract).

Over 1 in 10 people in the UK and around 10-15% of people globally are thought to have IBS, with symptoms ranging from mild to severe, and varying from person to person.

Symptoms can include flatulence, bloating, alternating diarrhoea and constipation, and stomach pains/cramping.

There is currently no cure for IBS. However, symptoms can usually be managed with lifestyle changes (e.g. diet). More severe symptoms may require medication.

If you think you may have IBS, it is important to speak to your GP who will be able to provide guidance on next steps.  

What are the symptoms of irritable bowel syndrome (IBS)?

Some of the most common symptoms of IBS include:

  • Flatulence
  • Bloating
  • Stomach pain and cramping
  • Changes in bowel habits – such as alternating diarrhoea and constipation
  • An urgent need to use the toilet

There is currently no specific test available to confirm or rule out IBS as the cause of these symptoms.

This means that healthcare professionals will usually try to rule out other digestive conditions that have similar symptoms, such as lactose intolerance and coeliac disease, before providing a diagnosis of IBS.

What is the difference between lactose intolerance and IBS?

Although both lactose intolerance and irritable bowel syndrome (IBS) share symptoms in common, there are a couple of fundamental differences that set the two conditions apart.

Causes

Lactose intolerance occurs when the body fails to produce enough of the lactase enzyme, which is required to break down lactose – a type of sugar found in milk and dairy products.

The symptoms of lactose intolerance (flatulence, bloating, stomach pains etc.) only occur when a person with lactose intolerance consumes dairy products (e.g. milk, cheese, cream, butter etc.).

However, this is not the case with IBS.

Potential causes of IBS can differ from person to person, and range from sensitivity to certain foods (e.g. fatty foods, spices, certain fruits and vegetables), to emotional stress and anxiety.

Dairy can also be a trigger for IBS, but this does not necessarily mean that the person is lactose intolerant.

Treatment

Although treatment for both lactose intolerance and IBS involves making changes to the diet, and may also require certain prescribed medications, treatment for IBS can also include lifestyle changes such as stress reduction and increased physical activity.

Despite the differences in causes and treatment of the two conditions, one thing that both lactose intolerance and IBS have in common is that, for the most part, a level of self-care is expected to lessen the symptoms and prevent further health complications.

In people with lactose intolerance, this means removing dairy products from the diet completely, and choosing lactose/dairy-free alternatives.

In people with IBS, it is often recommended that the person monitor their condition carefully, including any potential triggers for the symptoms (e.g. after eating certain foods).

If you are experiencing symptoms that could indicate lactose intolerance or irritable bowel syndrome (IBS), it is recommended that you speak to your GP who will be able to advise on next steps for securing a diagnosis.

Who is most at risk of lactose intolerance?

Some risk factors for developing lactose intolerance include:

  • Having a close family member who has been diagnosed with primary lactose intolerance – research shows that people with primary lactose intolerance have a higher risk of passing it down to first-degree relatives (i.e. parents to children)
  • Ancestry – research shows that people of Asian, African or Hispanic descent are at greater risk of developing lactose intolerance. Lactose intolerance is more common in parts of the world where dairy consumption is low
  • Having another form of intestinal disease such as coeliac disease or inflammatory bowel disease (IBD) – this can increase the risk of secondary lactose intolerance
  • Injury to the gut/small intestine – a common cause of secondary lactose intolerance
  • Infection, chemotherapy, and certain antibiotics – each of these can trigger secondary lactose intolerance. Although this form of lactose intolerance usually resolves itself, it can be permanent in some people
  • Premature birth – some babies born prematurely may be at increased risk of having developmental lactose intolerance

Who is most at risk of IBS?

Some risk factors for developing IBS include:

  • Lifestyle choices – poor diet, lack of exercise, smoking and drinking alcohol have been known to trigger IBS flare-ups
  • Infections of the digestive tract
  • Having another form of intestinal condition such as lactose intolerance, coeliac disease, or inflammatory bowel disease (IBD)
  • Having anxiety, depression or other mental health issues
  • Having a history of stress or trauma

The condition is also more common among women than men.

How is lactose intolerance diagnosed?

If you are experiencing symptoms that you suspect are due to lactose intolerance, the first step is to discuss your symptoms with your doctor, who will be able to offer advice and guidance on testing and treatment.

Testing for lactose intolerance can include:

  • hydrogen breath testing, conducted by measuring the level of hydrogen in your breath over several hours after consuming an oral solution of lactose
  • stool acidity testing, which measures the acidity of your stools (faeces), usually after dairy has been consumed
  • genetic testing using a DNA sample

An AlphaBiolabs Genetic Lactose Intolerance Test uses a simple cheek swab DNA sample to assess the likelihood of a person having primary lactose intolerance.

This type of lactose intolerance is hereditary, making genetic testing a useful tool for determining whether you are likely to have primary lactose intolerance.

You have a higher chance of having primary lactose intolerance if you have a first-degree relative (parent, child, sibling) with the condition.

How is IBS diagnosed?

There is currently no specific test available to confirm or rule out IBS as the cause of a person’s symptoms.

This means that healthcare professionals will usually screen for other conditions that have similar symptoms to IBS, such as lactose intolerance and coeliac disease.

If these conditions can be ruled out, a diagnosis of IBS may be reached.

Before seeing a doctor about suspected IBS, it is often recommended that the patient keep a diary prior to their appointment, which can help healthcare professionals identify potential triggers (e.g. certain foods) for the symptoms.

How is lactose intolerance treated?

There is no ‘cure’ for lactose intolerance, but symptoms can be managed by excluding lactose from the diet, taking medication to assist with lactose digestion, or consuming products that have had lactose removed or reduced.

Many people find that they can improve their quality of life by removing foods like milk, cheese, and yoghurt from their diet – all of which contain lactose.

However, lactose can also be found in very small quantities in other products such as supplements and medicines, so if you do have a lactose intolerance, it’s important to check labels to ensure that there is no lactose present.

Speak to your GP for further advice and guidance on managing lactose intolerance. 

How is IBS treated?

The treatment of IBS can vary from person to person, depending on symptoms.

However, it will often include dietary changes. Depending on the severity of the symptoms, your doctor may also prescribe medications.

Speak to your GP for further advice and guidance on managing IBS.

Can you have IBS and lactose intolerance at the same time?

It is possible to have both IBS and lactose intolerance at the same time.

IBS and lactose intolerance share many of the same symptoms, including flatulence, bloating and stomach pains.

Milk is also known to be a trigger for the symptoms of IBS, and many studies have shown that lactose intolerance is more common in people who have IBS, than in those who do not.

Buy a lactose intolerance test

Order your Genetic Lactose Intolerance Test direct from our award-winning, accredited laboratory.

Karolina Baker, AlphaBiolabs

Karolina Baker

Health Testing Specialist at AlphaBiolabs

Karolina joined AlphaBiolabs in 2021 and holds the role of Health Testing Specialist.

As well as overseeing a range of health tests, Karolina plays an active role in the research and development of the company’s latest health test offerings.

Before joining AlphaBiolabs, Karolina worked as an Associate Practitioner at Mid-Cheshire Hospitals NHS Foundation Trust, and as a research assistant at the Turner Laboratory, within the Faculty of Biology, Medicine and Health at The University of Manchester.

Karolina’s main scientific interests include clinical genomics and genetic diagnostics. Her qualifications include a BSc in Molecular Biology and an MSc in Genomic Medicine.

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