GLP 1 Medicines Explained: What Are They?
GLP 1 medicines have become one of the most talked about developments in weight management in recent years.
Names such as Wegovy, Mounjaro and Ozempic now appear regularly in newspapers, on social media and in conversations about weight loss.
But what exactly is a GLP 1 medicine?
And why can medicines originally associated with diabetes also affect appetite and body weight?
GLP 1 medicines work by copying or enhancing the effects of hormones that are naturally involved in appetite, digestion and blood sugar control.
Some are licensed specifically for weight management, some are licensed for type 2 diabetes, and some have different licensed uses depending on the particular medicine and product.
They are prescription only medicines and are not appropriate for everyone.
What Does GLP 1 Mean?
GLP 1 stands for glucagon like peptide 1.
It is a hormone naturally released by the digestive system after eating.
Among other things, GLP 1 helps:
Signal that you have eaten Increase feelings of fullness Influence appetite Slow the movement of food through the stomach Support insulin release when blood sugar rises Help regulate blood glucose
Medicines that act on this system are often called GLP 1 receptor agonists.
They activate the same receptors that the natural GLP 1 hormone acts upon.
The result can be reduced hunger, greater feelings of fullness and improved blood sugar control.
Are All GLP 1 Medicines the Same?
No.
This is where some of the terminology becomes confusing.
Several medicines are grouped together when people talk about GLP 1 treatment, but they do not all work in exactly the same way.
Semaglutide
Semaglutide acts on the GLP 1 receptor.
Different semaglutide products are licensed for different purposes.
For example:
Wegovy is used for weight management in appropriate patients.
Ozempic is used for type 2 diabetes.
The fact that two medicines contain the same active ingredient does not mean that they have the same licensed indication, dose or treatment pathway.
Liraglutide
Liraglutide is another medicine that acts on the GLP 1 receptor.
It has been used in both diabetes and weight management treatment depending on the particular product and indication.
Unlike some newer weekly medicines, liraglutide is normally administered daily.
Tirzepatide
Tirzepatide is slightly different.
It acts on two hormone systems rather than one.
These are:
GLP 1
and
GIP, which stands for glucose dependent insulinotropic polypeptide.
This is why tirzepatide is sometimes referred to as a dual GIP and GLP 1 receptor agonist rather than simply a GLP 1 medicine.
Mounjaro contains tirzepatide.
How Do GLP 1 Medicines Help With Weight Management?
One of their main effects is on appetite.
These medicines can help people feel fuller after eating and remain satisfied for longer.
For some people this can lead to:
Reduced hunger Smaller portions Less frequent snacking Reduced interest in food Feeling full sooner during meals Less persistent thinking about food
This can make it easier to consume less energy without relying entirely on deliberate restriction.
However, GLP 1 medicines do not directly remove body fat simply because someone has taken an injection or tablet.
Weight loss occurs because several effects of treatment can influence appetite and food intake over time.
NICE recommends that weight management medicines are used alongside appropriate dietary changes and increased physical activity rather than as a complete replacement for them.
What Is Food Noise?
You may have heard people using the phrase food noise when discussing GLP 1 medicines.
It is not a formal medical diagnosis.
People generally use it to describe persistent thoughts about food.
For example:
Thinking about your next meal soon after eating Constantly noticing food Frequent cravings Finding it difficult to stop thinking about snacks Feeling that food occupies a large amount of mental space
Some people taking appetite regulating medicines report that these thoughts become less noticeable.
Experiences vary considerably.
Not everyone has strong food related thoughts before treatment, and not everyone experiences the same change afterwards.
Do GLP 1 Medicines Slow Digestion?
They can slow the rate at which food leaves the stomach.
This contributes to feeling fuller for longer.
It also helps explain some of the digestive side effects associated with treatment.
Possible gastrointestinal effects can include:
Nausea Vomiting Constipation Diarrhoea Abdominal discomfort Indigestion Feeling unusually full
These effects are among the reasons treatment doses are often increased gradually rather than starting immediately at a higher dose.
Why Are GLP 1 Doses Increased Slowly?
Many GLP 1 based treatments use a dose escalation period.
This means treatment begins at a lower dose and is gradually increased according to the licensed dosing schedule and the patient's clinical response.
The lower initial dose gives the body time to adjust.
Starting at a much higher dose could increase the likelihood of gastrointestinal side effects.
The starting dose is not necessarily intended to be the long term maintenance dose.
Dose decisions should be made by the prescribing clinician.
Patients should not increase their dose early simply because they want faster weight loss.
Are GLP 1 Medicines Insulin?
No.
GLP 1 medicines are not insulin.
They affect some of the same systems involved in blood sugar regulation, but they are different types of medication.
GLP 1 activity can increase insulin secretion when blood glucose levels are elevated.
This is one reason some medicines in this group are used to treat type 2 diabetes.
Do You Need Diabetes to Use a GLP 1 Medicine for Weight Management?
Not necessarily.
Some GLP 1 related medicines have specific UK authorisations for weight management.
A person does not automatically need type 2 diabetes to be considered for one of those treatments.
However, eligibility depends on the specific medicine and the person's circumstances.
Factors can include:
BMI Weight related health conditions Medical history Current medication Previous treatment Pregnancy or plans for pregnancy Potential risks and benefits
Meeting a BMI threshold does not automatically guarantee a prescription.
A clinician still needs to decide whether treatment is safe and appropriate.
You can read more in our guide:
Who Can Be Prescribed Weight Loss Medication in the UK?
What Is the Difference Between Wegovy and Ozempic?
This is one of the most common sources of confusion.
Both contain semaglutide.
However, they are not interchangeable brand names for the same treatment purpose.
Wegovy is authorised for weight management in appropriate patients.
Ozempic is authorised for the treatment of type 2 diabetes.
The MHRA specifically advises that not every GLP 1 medicine is authorised for weight loss simply because the medicine belongs to this group.
A medicine should be prescribed according to an appropriate clinical assessment and its relevant authorised use.
Is Mounjaro a GLP 1 Medicine?
It is frequently grouped with GLP 1 medicines, but technically it acts on both GIP and GLP 1 receptors.
Its active ingredient is tirzepatide.
Like semaglutide, it can influence appetite and feelings of fullness.
NICE includes tirzepatide among the medicine options used for weight management in appropriate adults.
Are GLP 1 Medicines Only Available as Injections?
Not all of them.
Many of the best known weight management treatments are supplied in prefilled injection pens.
However, GLP 1 related medicines can also exist in tablet form depending on the specific medicine, indication and authorised product.
The MHRA advises that legitimate GLP 1 medicines may be supplied in authorised injection pens or tablet form.
It also warns against products sold as powders that need to be mixed before injection where these are not authorised medicines.
How Often Are GLP 1 Injections Taken?
It depends on the medicine.
Some treatments are used once weekly.
Others are used once daily.
For example, semaglutide and tirzepatide weight management injections are generally administered once each week, while liraglutide has traditionally been used daily.
Always follow the dosing instructions provided for the medicine you have actually been prescribed.
Where Are GLP 1 Injections Given?
For medicines supplied as self injection pens, treatment is usually injected under the skin.
Common injection areas can include:
Abdomen Thigh Upper arm
The exact instructions depend on the medicine.
Patients should follow the product instructions and guidance provided by their healthcare professional rather than relying on instructions for a different injection.
Who Can Prescribe GLP 1 Medicines?
GLP 1 medicines are prescription only medicines.
This means a suitable healthcare professional must assess the patient before issuing a prescription.
The MHRA states that private access should involve a consultation and appropriate checks before prescribing so that the risks and benefits can be assessed.
A legitimate weight management service should therefore not simply allow someone to purchase prescription medicine without a proper assessment.
Can You Buy GLP 1 Medicines Privately?
Yes, certain medicines may be prescribed privately where they are clinically appropriate.
But private treatment does not remove the requirement for medical assessment.
A prescriber may consider:
Your weight and height Medical conditions Current medicines Previous reactions to treatment Relevant family history Other weight related conditions Potential contraindications Whether the treatment is likely to be suitable
Paying privately does not guarantee that a particular medicine will be prescribed.
Can You Get GLP 1 Medicines Through the NHS?
Some GLP 1 related medicines are available through NHS pathways for diabetes or weight management where the relevant criteria are met.
NICE recommends several medicines as options for weight management in particular groups of adults, including tirzepatide, semaglutide and liraglutide.
However, the criteria for accessing treatment through the health service can be more restrictive than the broader licensed indication for the medicine.
Access also varies across the UK.
What About Northern Ireland?
Northern Ireland has historically had more limited specialist obesity services than some other parts of the UK.
A new Regional Obesity Management Service is being introduced, with access initially focused on people with higher levels of clinical need.
This means someone may potentially meet the licensed criteria for private medical weight management while not currently meeting the criteria for publicly funded treatment in Northern Ireland.
You can read more in:
Can You Get Weight Loss Treatment on the NHS in Northern Ireland?
and
Northern Ireland's New Obesity Management Service: Who Qualifies and How Will It Work?
What Are the Common Side Effects?
Side effects vary between medicines and patients.
Gastrointestinal symptoms are among the most commonly discussed.
These can include:
Nausea Vomiting Diarrhoea Constipation Abdominal discomfort Indigestion
Some people may also experience:
Headache Fatigue Dizziness Reduced appetite
Side effects can sometimes be more noticeable while the dose is being increased.
Not everyone experiences side effects, and their severity can vary considerably.
Can GLP 1 Medicines Cause Serious Side Effects?
Serious adverse effects are less common, but they can occur.
The MHRA has strengthened warnings around acute pancreatitis for GLP 1 receptor agonists and dual GIP and GLP 1 medicines.
Severe and persistent abdominal pain, particularly if it radiates towards the back and is accompanied by nausea or vomiting, requires urgent medical assessment.
Patients should read the patient information supplied with their medicine and know when to contact their clinician or seek urgent help.
Can GLP 1 Medicines Make You Tired?
Yes, fatigue can occur with some treatments.
But tiredness during weight management may also result from:
Eating too little Dehydration Vomiting or diarrhoea Poor sleep Nutritional deficiencies Other medical conditions
You can read our full guide:
Can Weight Loss Medication Make You Tired?
Can You Drink Alcohol While Taking GLP 1 Medication?
Alcohol is not automatically prohibited for everyone using these medicines.
However, it can complicate weight management and may worsen symptoms such as nausea or dehydration for some people.
Alcohol can also affect blood sugar, particularly for people with diabetes who use other glucose lowering medicines.
If you are unsure how alcohol interacts with your particular treatment or medical conditions, ask your prescribing clinician.
What Happens If You Stop Taking GLP 1 Medication?
The appetite reducing effects gradually diminish once treatment is stopped and the medicine leaves the body.
For some people, hunger and food related thoughts become more noticeable again.
Research has also shown that weight regain can occur after weight management medicines are discontinued.
This does not mean that treatment has failed.
It highlights the importance of thinking about long term weight management rather than treating medication as a temporary quick fix.
Read more:
Do You Need to Taper Off Weight Loss Medication?
Do GLP 1 Medicines Permanently Change Your Metabolism?
They should not be thought of as permanently resetting the metabolism.
Their effects are largely associated with the period during which treatment is active.
They influence appetite, digestion and glucose regulation while the medicine is present.
Weight maintenance after treatment may therefore require continued attention to eating patterns, physical activity, sleep and other behaviours.
Can GLP 1 Medicines Replace Healthy Eating?
No.
Medication can make appetite easier to manage for some people, but nutritional quality still matters.
When appetite is substantially reduced, it can actually become more important to make smaller meals nutritionally useful.
Useful priorities include:
Protein Vegetables Fruit Fibre Adequate fluids Appropriate portions
A person who eats very little but consumes a poor quality diet may still fall short of important nutrients.
What About Exercise?
Physical activity remains important.
It supports:
Cardiovascular health Fitness Mental wellbeing Mobility Muscle maintenance Long term weight management
Resistance exercise can be particularly useful during weight loss because some lean tissue can be lost alongside body fat.
The aim does not need to be spending every evening in a gym.
Walking, resistance exercises and general daily movement can all contribute.
Are GLP 1 Medicines a Quick Fix?
They should not be treated as one.
The MHRA specifically warns that these medicines are prescription treatments intended for appropriate medical use rather than cosmetic or rapid weight loss.
For suitable patients, they can form part of a wider weight management strategy.
But they still require:
Appropriate assessment Monitoring Dose management Awareness of side effects Nutrition Physical activity Longer term planning Are GLP 1 Medicines Safe to Buy Online?
They can be obtained legitimately through regulated online healthcare services and pharmacies.
However, there is also a significant illegal market.
The MHRA warns people not to purchase these medicines from unregulated sellers, beauty salons, social media accounts or websites that supply them without a clinical consultation. Fake products have been associated with serious health risks.
Prescription weight management medicines should come through legitimate healthcare and pharmacy channels.
If a website is willing to sell a prescription medicine without asking meaningful medical questions, that should be a warning sign.
What Should a Proper Online Assessment Include?
An online service should gather enough information for the prescriber to make a safe decision.
That may include:
Height Weight Medical history Current medication Allergies Previous weight management treatment Relevant health conditions Pregnancy or plans for pregnancy where appropriate Verification of identity and weight where necessary
The clinician may also request additional information before deciding whether treatment is appropriate.
Online prescribing should still be clinical prescribing. It should not be automatic.
How Does Keltoi Approach Weight Management?
Keltoi Wellness provides a doctor led remote weight management service for adults in Northern Ireland.
Patients provide health and weight information through a secure assessment process.
That information is reviewed before any prescription decision is made.
Where prescription treatment is being considered, the final choice of treatment and dose belongs to the prescribing doctor and is based on the individual patient's circumstances.
A patient's preference for a particular treatment does not guarantee that it will be prescribed.
The Bottom Line
GLP 1 medicines work by acting on hormone pathways involved in appetite, fullness, digestion and blood sugar regulation.
Medicines in this area include semaglutide and liraglutide, while tirzepatide acts on both GIP and GLP 1 receptors.
Some products are authorised for weight management, some for type 2 diabetes, and the exact indication depends on the medicine and product.
For suitable patients, these medicines can support weight management by reducing hunger and increasing feelings of fullness.
However, they are prescription only medicines rather than general weight loss products.
They are not suitable for everyone, can cause side effects and should only be used following an appropriate clinical assessment.
Keltoi Wellness provides doctor led weight management support remotely for adults across Northern Ireland.
Any prescription treatment is subject to an individual clinical assessment, with prescribing decisions made independently by the treating doctor.
Health information provided by Keltoi Wellness is for general education and does not replace individual medical advice, diagnosis or treatment.