GLP-1 Diabetes Treatments: Benefits and Side Effects

GLP-1 diabetes treatments have transformed the management of type 2 diabetes, offering meaningful blood sugar control alongside cardiovascular and weight benefits. GLP-1 receptor agonists work by mimicking a natural gut hormone to stimulate insulin release, suppress glucagon, and slow digestion. Medicines in this class include semaglutide (Ozempic, Wegovy), liraglutide (Victoza), dulaglutide (Trulicity), and tirzepatide (Mounjaro). This article explains how these medicines work, who can access them on the NHS, how they compare with other treatments, what side effects to watch for, and what current NICE guidance recommends.

How do GLP-1 medicines help control blood sugar in type 2 diabetes?

GLP-1 receptor agonists lower blood sugar by stimulating glucose-dependent insulin release, suppressing glucagon, and slowing gastric emptying. Specific agents such as liraglutide, semaglutide, and dulaglutide have also demonstrated cardiovascular outcome benefits in large trials.

GLP-1 receptor agonists lower blood sugar in type 2 diabetes by mimicking the action of glucagon-like peptide-1, a hormone released naturally from the gut after eating. This hormone stimulates the pancreas to release insulin in response to rising glucose levels, suppresses glucagon secretion (which would otherwise raise blood sugar), and slows gastric emptying so that glucose enters the bloodstream more gradually. Because insulin release is glucose-dependent, the risk of hypoglycaemia is considerably lower than with some older drug classes such as sulphonylureas. However, when GLP-1 receptor agonists are used alongside insulin or a sulphonylurea, the risk of hypoglycaemia increases, and the dose of the insulin or sulphonylurea may need to be reviewed by the prescriber.

The medicines in this class include semaglutide (available as Ozempic for type 2 diabetes and Wegovy for weight management), liraglutide (Victoza for diabetes, Saxenda for weight management), dulaglutide (Trulicity), exenatide (Byetta and Bydureon), and tirzepatide (Mounjaro). Tirzepatide acts on both GLP-1 and GIP receptors, giving it a dual mechanism.^[6][4] In the SURPASS clinical trial programme, tirzepatide produced pronounced reductions in HbA1c and body weight. The MHRA has authorised Mounjaro both for type 2 diabetes and for chronic weight management.^[10][11]

Beyond glucose lowering, GLP-1 receptor agonists reduce appetite and promote a feeling of fullness, which often leads to meaningful weight loss. This is clinically relevant in type 2 diabetes, where excess weight is a major driver of insulin resistance. Specific agents in this class have also demonstrated cardiovascular benefits in large outcome trials: liraglutide in the LEADER trial, semaglutide in SUSTAIN-6, and dulaglutide in the REWIND trial each showed reductions in major adverse cardiovascular events in people with established cardiovascular disease or high cardiovascular risk.^[8] These benefits are agent-specific and should not be assumed to apply to the class as a whole.

Which GLP-1 drugs are available on the NHS and who can get them?

Several GLP-1 receptor agonists, including semaglutide, liraglutide, dulaglutide, and tirzepatide, are available on the NHS for type 2 diabetes, subject to NICE technology appraisal criteria and local ICB commissioning decisions.

Several GLP-1 receptor agonists are available on the NHS for type 2 diabetes, subject to local Integrated Care Board (ICB) commissioning decisions and prescriber assessment. Agents that have received NICE recommendations for use within the NHS include semaglutide (Ozempic, TA772), liraglutide (Victoza), dulaglutide (Trulicity, TA622), and exenatide prolonged-release. Tirzepatide (Mounjaro) has been recommended by NICE for type 2 diabetes in specific circumstances, and NHS availability depends on whether the local ICB has implemented that guidance. Patients and clinicians should refer to the current NICE technology appraisals and local ICB commissioning policies, as these are updated as new evidence emerges.

Eligibility typically depends on a number of clinical factors, including:

• HbA1c level that remains above target despite existing treatment

• Body mass index (BMI), with some guidance specifying thresholds

• Cardiovascular risk or established cardiovascular disease, which may strengthen the case for certain agents

• Tolerability of or contraindications to other glucose-lowering medicines

For weight management rather than diabetes, Wegovy (semaglutide) and Mounjaro (tirzepatide) are available through specialist NHS weight management services, typically requiring referral to a Tier 3 or equivalent specialist service, again subject to ICB commissioning. Saxenda (liraglutide) has also been used in this context. Patients seeking access through a private route should ensure they use a regulated provider. Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, where a medicine such as Mounjaro may be considered if it is clinically appropriate.

Anyone unsure whether they qualify for NHS treatment should speak to their GP or diabetes care team, who can assess eligibility and initiate a referral or prescription where indicated.

How well do GLP-1 treatments work compared to other diabetes medicines?

GLP-1 receptor agonists are among the most effective glucose-lowering agents for type 2 diabetes, often matching or exceeding DPP-4 inhibitors in HbA1c reduction while also producing significant weight loss. Tirzepatide showed particularly strong results versus semaglutide in the SURPASS-2 trial.

GLP-1 receptor agonists are among the most effective glucose-lowering agents available for type 2 diabetes, and they also offer benefits beyond HbA1c reduction that many older medicines do not. In head-to-head and placebo-controlled trials, agents such as semaglutide and dulaglutide have produced clinically meaningful reductions in HbA1c, often comparable to or exceeding those seen with dipeptidyl peptidase-4 (DPP-4) inhibitors and sodium-glucose cotransporter-2 (SGLT-2) inhibitors, while also delivering significant weight loss. It is worth noting that combining a GLP-1 receptor agonist with a DPP-4 inhibitor is generally not recommended, as both act through overlapping mechanisms; the BNF and NICE guidance advise against routine co-prescribing.^[15][5]

Tirzepatide (Mounjaro), with its dual GLP-1 and GIP receptor activity, demonstrated particularly strong HbA1c reductions and substantial body weight reduction in the SURPASS-2 trial, which compared it directly with semaglutide 1 mg weekly. Individual response varies and tolerability must always be considered when selecting treatment.

Importantly, specific GLP-1 receptor agonists have demonstrated cardiovascular outcome benefits in large randomised trials, as noted above. SGLT-2 inhibitors share some cardiovascular and renal protective properties, and NICE guidance (NG28) considers both classes when selecting add-on therapy, with the choice guided by individual clinical circumstances rather than a fixed treatment step.

The main practical disadvantages of GLP-1 medicines compared with oral agents are the injectable route of administration (for most formulations), the gastrointestinal side effect profile, and cost. Oral semaglutide (Rybelsus) is available for type 2 diabetes and offers an alternative for those who prefer not to inject, though its dosing requirements and administration conditions differ from injectable formulations and patients should follow the instructions in the product leaflet.

What side effects should you watch for when taking a GLP-1 medication?

The most common side effects are gastrointestinal, including nausea, vomiting, and diarrhoea, which typically improve over several weeks. Serious but rarer risks include acute pancreatitis and gallbladder problems, requiring prompt medical attention if symptoms develop.

The most common side effects of GLP-1 receptor agonists are gastrointestinal, and these are most likely to occur when starting treatment or after a dose increase. Patients frequently report:

• Nausea, which is often mild to moderate and tends to improve over several weeks

• Vomiting and diarrhoea, particularly in the early weeks of treatment

• Constipation and reduced appetite

• Injection site reactions such as redness, bruising or itching

Starting at a low dose and escalating gradually, as recommended in the prescribing information, helps to minimise these effects. Eating smaller meals, avoiding high-fat or spicy foods, and staying well hydrated can also reduce gastrointestinal discomfort. If persistent vomiting or diarrhoea means you are unable to keep fluids down, seek urgent clinical advice, as dehydration can affect kidney function.

Acute pancreatitis has been reported with GLP-1 receptor agonists, including post-marketing reports of necrotising pancreatitis and reports with a fatal outcome.^[19] Patients should seek prompt medical attention if they develop persistent, severe abdominal pain, particularly if it radiates to the back. Treatment should be discontinued if pancreatitis is confirmed. Patients with a personal or family history of pancreatitis should discuss this with their prescriber before starting.

Gallbladder problems, including gallstones (cholelithiasis) and gallbladder inflammation (cholecystitis), have been reported with medicines in this class. Seek medical advice if you develop severe pain in the upper abdomen, fever, or yellowing of the skin or eyes.

When GLP-1 receptor agonists are used alongside insulin or a sulphonylurea, the risk of hypoglycaemia is increased. Your prescriber may reduce the dose of the insulin or sulphonylurea when starting a GLP-1 medicine.

Because these medicines slow gastric emptying, they may affect how quickly some other oral medicines are absorbed. Tell your prescriber or pharmacist about all medicines you are taking so that any interactions can be reviewed.

GLP-1 receptor agonists are not recommended during pregnancy or breastfeeding. If you are pregnant, planning a pregnancy, or breastfeeding, discuss this with your prescriber before starting or continuing treatment.

For people with pre-existing diabetic eye disease, particularly those with pre-proliferative or proliferative retinopathy, rapid improvement in blood glucose control may be associated with transient worsening of diabetic retinopathy. This risk should be discussed with the diabetes care team before initiating treatment in this subgroup.

Suspected adverse reactions to GLP-1 medicines can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. If you experience symptoms that concern you, contact your GP or call NHS 111 for urgent advice. Call 999 only in a life-threatening emergency.

What does NICE say about using GLP-1 therapies for type 2 diabetes?

NICE guideline NG28 recommends GLP-1 receptor agonists as an intensification option when existing therapy is insufficient, with earlier use supported for those with established cardiovascular disease. Individual agents are assessed through separate NICE technology appraisals.

NICE recommends GLP-1 receptor agonists as an option for adults with type 2 diabetes whose blood glucose is not adequately controlled on existing therapy, particularly when weight management is a clinical priority or when cardiovascular risk is elevated. The relevant guidance is set out primarily in NICE guideline NG28 (Type 2 diabetes in adults: management), which is updated periodically to reflect new evidence and newly recommended medicines.

NICE guidance positions GLP-1 receptor agonists as an intensification option when existing therapy is insufficient, though current NG28 wording emphasises individualised care rather than a rigid treatment step. For people with established atherosclerotic cardiovascular disease, earlier consideration of agents with proven cardiovascular benefit is supported by the evidence and reflected in NICE guidance. NICE technology appraisals have individually assessed agents including semaglutide (TA772), dulaglutide (TA622), and tirzepatide (Mounjaro), with recommendations specifying the clinical criteria under which each is recommended for NHS use. Whether a specific medicine is commissioned locally is ultimately a decision for the relevant ICB.

For weight management in people with obesity and type 2 diabetes, NICE has also issued guidance on semaglutide (Wegovy) and tirzepatide (Mounjaro), recognising the overlap between the two conditions. The injectable Wegovy formulation is available in weekly doses up to 2.4 mg, with a higher 7.2 mg weekly injectable strength also authorised. Following MHRA authorisation in June 2026, oral semaglutide for weight management is available as Wegovy 25 mg tablets, which is a distinct product from Rybelsus with its own licensed posology; patients should follow the dosing schedule specified in the product leaflet for whichever formulation they are prescribed.

Patients and clinicians should always refer to the most current published NICE guidance and local ICB commissioning policies, as recommendations evolve as new evidence emerges. Your GP or diabetes specialist nurse is the best starting point for understanding which options apply to your individual circumstances.

Scientific References

1. Ozempic 0.5 mg solution for injection in pre-filled pen.
2. Summary of NICE guidance for GLP-1 receptor agonists and tirzepatide in adults (NG28 resource).
3. Semaglutide: a medicine to manage type 2 diabetes or obesity.
4. Tirzepatide | Drugs | BNF — NICE.
5. Semaglutide | Drugs | BNF — NICE.
6. GLP-1 medicines for weight loss and diabetes: what you need to know.
7. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes (SUSTAIN-6). Marso SP et al..
8. Liraglutide and Cardiovascular Outcomes in Type 2 Diabetes (LEADER). Marso SP et al..
9. Dulaglutide and cardiovascular outcomes in type 2 diabetes (REWIND). Gerstein HC et al..
10. MHRA authorises diabetes drug Mounjaro (tirzepatide) for weight management and weight loss.
11. Mounjaro | European Medicines Agency (EMA).
12. Semaglutide for managing overweight and obesity (TA875).
13. Further medication | Type 2 diabetes in adults: management (NG28).
14. Type 2 diabetes in adults: management (NG28).
15. Type 2 diabetes in adults: choosing, reviewing and stopping medicines — visual summary (NG28 resource).
16. Initial medicines | Type 2 diabetes in adults: management (NG28).
17. Type 2 diabetes in adults: management — recommendations (NG28).
18. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). Frías JP et al..
19. GLP-1 receptor agonists and dual GLP-1/GIP receptor agonists: strengthened warnings on acute pancreatitis including necrotising and fatal cases.
20. GLP-1 receptor agonists: reminder of the potential side effects and to be aware of the potential for misuse.
21. Association of Glucagon-Like Peptide-1 Receptor Agonist Use With Risk of Gallbladder and Biliary Diseases: A Systematic Review and Meta-analysis of Randomized Clinical Trials..
22. NG242 Diabetic retinopathy: management and monitoring — evidence review C (effectiveness of intensive treatments to lower blood glucose levels).
23. Medicines regulator approves up to 7.2 mg dose of semaglutide/Wegovy for patients with obesity.
24. Wegovy | European Medicines Agency (EMA).
25. Mechanisms of action and therapeutic applications of GLP-1 and dual GIP/GLP-1 receptor agonists..
26. Trulicity 0.75 mg solution for injection in pre-filled pen — EMA product information.

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