Supporting patients on weight loss medications: a practical guide for pharmacists

Dr Waseem Majeed, Lead Consultant Endocrinologist at Oviva, explains some of the key issues for community and practice pharmacists in prescribing of weight-loss medications

The UK is facing an obesity crisis. More than a quarter of the English population are living with obesity and it is a major risk factor for many common cancers and conditions such as heart attacks, stroke and type 2 diabetes. Obesity is estimated to cost the NHS over £19 billion a year.

New weight loss medications are changing how we treat both type 2 diabetes and obesity. Widening access to these innovative weight loss drugs has huge potential to reduce pressures on the NHS – saving as much as £52 billion by 2050 – as well as helping people to lead healthier lives.

As these medications become more widely available, pharmacists will play an increasingly important role in helping patients use these treatments safely and effectively. This includes helping patients understand how the drugs work, managing side effects and ensuring they get the lifestyle and nutrition support needed for long-term success.

How these medications work

Semaglutide – or more commonly known as Ozempic and Wegovy – works by mimicking a hormone called glucagon-like peptide-1 (GLP-1) that helps control blood sugar, reduces appetite and slows down how quickly food leaves the stomach. This helps people feel fuller for longer, eat less and lose weight. Originally developed to treat type 2 diabetes, these medications have been shown to support significant, sustainable weight loss when combined with healthy lifestyle changes.

Tirzepatide – known as Mounjaro – is also a type 2 diabetes medication and works in a similar way but mimics two gut hormones instead of one – GLP-1 and GIP (glucose-dependent insulinotropic polypeptide); studies suggest that by affecting two hormones, tirzepatide may result in slightly greater weight loss, although the specific impact of mimicking GIP remains the subject of ongoing research.

Who can take them?

NICE has approved the use of semaglutide and tirzepatide for individuals with a BMI over 35 kg/m² and at least one weight-related comorbidity, such as type 2 diabetes, prediabetes, hypertension, cardiovascular disease or obstructive sleep apnoea. These medications are recommended as part of a comprehensive approach that includes a reduced-calorie diet and increased physical activity to support long-term weight management and health improvement.

NICE recommends that semaglutide is prescribed within the NHS for a maximum of two years, in combination with multidisciplinary support delivered through specialist weight management services. In contrast, NICE has approved tirzepatide for use both in specialist services and, in time, primary care settings, as part of a phased implementation. Initial access via primary care will be limited to individuals with class 3 obesity (BMI >40 kg/m²) and at least four qualifying comorbidities. Notably, unlike previous guidance for comparable therapies, NICE has not imposed a fixed two-year treatment limit for tirzepatide.

Note that where community pharmacists are prescribing weight-loss medications privately, the General Pharmaceutical Council advises that pharmacists prescribing remotely must independently verify the information the person provides on height, weight and/or BMI, through ‘video consultation, in person, from the person’s clinical records or by contacting another healthcare provider such as the person’s GP’. Patients can be encouraged to share their GP record with the pharmacist to simplify that process.

What pharmacists should know when advising patients

These injections are usually started at a low dose and gradually titrated over several weeks, with dose increments typically occurring every four weeks. The most common side effects are:

• Nausea.
• Vomiting.
• Diarrhoea.
• Constipation.
• Abdominal pain.
• Tiredness.
• Headache.
• Bloating.

These side effects typically occur when treatment begins or the dose is increased but generally subside with time. Most side effects can be managed by supporting patients with reassurance and simple lifestyle advice. For example, patients should be encouraged to:

• Eat smaller meals.
• Avoid heavy or greasy food.
• Avoid lying down after a meal.
• Drink plenty of water.
• Avoid alcohol.

Some patients may require additional treatments such as an anti-emetic or laxative to help manage side effects.

There are also a few red flags to watch out for. In particular, if a patient develops severe abdominal pain or discomfort, they should seek urgent medical advice as this could be a sign of something more serious like pancreatitis which is a recognised, albeit rare, side effect of these medications.

Making the most of these medications with behaviour change

These pharmacotherapies are most effective when combined with multidisciplinary support.  This includes proactive management of side effects, psychological support and behavioural coaching on diet and physical activity. Sustained clinical benefit depends on achieving and maintaining weight loss. This can help patients to better embed lifestyle changes that endure beyond the course of medication, to help maximise long term outcomes. Abrupt discontinuation of treatment should be avoided as this can trigger rapid rebound weight gain and reverse metabolic improvements.

As these treatments reduce appetite and drive calorie deficit, the focus of dietary intervention has shifted to supporting patients with regular, nutrient dense meals. Meal plans should supply the right balance of macro and micronutrients to maintain lean mass, support metabolic health and minimise treatment-related adverse effects.

Here are some simple messages to share with patients:

• Eat enough protein: This helps protect muscle (loss of muscle mass is thought to be one of the side effects of the rapid weight loss seen with these medications) and promotes satiety. Including a good protein source with each meal can help to achieve this.
• Eat enough fibre: This helps promote satiety and can help manage some of the common side effects such as constipation. Remember the BGBGS (beans, greens, berries, grains and seeds).
• Eat complex carbohydrates: These provide lasting energy as they combine carbohydrates with fibre. They are digested more slowly than simple carbohydrates and so keep people full for longer. They include brown rice, quinoa and whole wheat pasta.
• Stay hydrated: Drinking enough water is important, especially when eating less.
• Don’t skip meals completely: Even if they are not very hungry, it’s important to have regular meals to keep energy stable and prevent nutritional deficits, and to create a healthy eating pattern that is sustainable in the long term.
• Increase physical activity: Patients should aim to stay active through regular physical activity – whether it is walking, swimming, cycling or another low-impact activity. Regular physical activity can help maintain a healthy weight in the long term. Given the concerns around muscle loss, patients should be encouraged to include regular strengthening and resistance exercise (twice per week) in their routines.

What about other medications?

Because these injections affect how the body digests food, they might change how other medicines are absorbed, and there may be other interactions with some medicines.

For example, these are some of the medicines to look out for:

• Oral contraceptive pill and HRT: The UK’s regulatory body for medicines, the Medicines and Healthcare products Regulatory Agency (MHRA), has warned that these medicines should not be taken during pregnancy or just before trying to get pregnant due to a lack of safety data. There are also concerns that tirzepatide in particular can reduce the effectiveness of oral contraceptives; patients may be encouraged to consider non-oral forms of contraception such as a coil or may need to use additional barrier contraception, especially in the four weeks after starting the medication or the four weeks after any dose increase. The British Menopause Society has also stated that weight loss injections can affect how well the body absorbs oral medications like HRT; in particular there is concern that reduced absorption of oral progestogens may provide inadequate endometrial protection. It has been suggested that enquiry about use of weight loss injections should be part of annual contraception and HRT reviews.
• Medications with narrow therapeutic indices: It is well established that long-acting, high strength incretin-based therapies such as semaglutide and tirzepatide delay gastric emptying, which may in turn affect the absorption of a range of orally administered medications. As a precaution, particular attention should be paid when these agents are used in individuals taking immunosuppressive or anti-rejection therapies, where even minor changes in bioavailability could compromise therapeutic efficacy or safety. Although specific data on drug–drug interactions with these classes of medication remain limited, current clinical practice in specialist centres is to undertake appropriate monitoring – especially during initiation and dose titration – until a more robust evidence base becomes available. Additionally, patients on warfarin may require more frequent INR monitoring after starting treatment or during dose adjustments, as altered absorption may affect anticoagulant stability.¹ In patients taking these agents, careful monitoring and, where appropriate, specialist input is advised.
• Other diabetes medicines like sulfonylureas: These can cause low blood sugar when used with semaglutide or tirzepatide; therefore, diabetic medications and doses must be reviewed in full when starting or titrating these weight loss medications and may need adjustment.

Are these drugs safe and effective in the long term?

NICE has approved the use of these weight-loss medications alongside a reduced-calorie diet and increased physical activity, recognising them as both clinically and cost effective.

At NHS provider Oviva, our clinical outcomes data show that patients prescribed Wegovy achieve an average weight loss of 15% of their initial body weight after 12 months.² Patients are intensively supported by a multidisciplinary team including doctors, dietitians and psychologists. These results mirror those seen in clinical trials, demonstrating that with the right behavioural and psychological support, real-world outcomes can match controlled study results.

GLP-1 receptor agonists (RAs) also appear to offer benefits beyond weight loss and glucose control. An analysis of a large database of US veterans linked treatment to lower risk across 42 conditions, including cardiovascular, renal and neurological diseases.³ Mild gastrointestinal and musculoskeletal side effects were slightly more common with GLP-1/GLP-1-GIP RAs.

In a large, randomised, placebo-controlled trial, once-weekly semaglutide reduced the relative risk of heart attack, stroke and cardiovascular death by approximately 20% in individuals with obesity and established cardiovascular disease.⁴ Additionally, a large registry study suggested a potential reduction in cancer risk among GLP-1 RA users independent of weight loss,⁵ raising the possibility of additional biological effects beyond weight reduction alone.

While these findings are compelling, much of the evidence remains observational and involves varied agents. Robust trials and long-term surveillance are needed to define the full scope of benefit and risk.

In the case of newer GLP-1/GIP RAs, growing evidence suggests tirzepatide delivers sustained, clinically significant weight loss, with a favourable safety and tolerability profile. Long-term success does not depend on continued pharmacotherapy alone, however. It is essential that patients develop and sustain healthier eating and lifestyle modifications while on treatment, enabling them to maintain weight loss even after stopping the medication.

While GLP-1 and GLP-1/GIP RAs show considerable promise, emerging safety concerns warrant attention. The MHRA has advised caution with their use in the perioperative setting due to the risk of aspiration from delayed gastric emptying, gastric content retention and vomiting, despite adequate fasting. Although the MHRA does not specify a formal cessation interval, many centres advise discontinuing these agents at least one week before procedures involving general anaesthesia. Patients scheduled for surgery should be referred back to their local teams to follow institution-specific preoperative protocols.

Additionally, although rarely, GLP-1 and GLP-1/GIP RAs have been associated with cases of acute pancreatitis and intestinal obstruction.⁶ As use of these therapies increases, it is essential that healthcare professionals remain aware of evolving safety guidance accordingly.

We are witnessing a major transformation in the treatment of obesity and type 2 diabetes, driven by the introduction of GLP-1 and GLP-1/GIP RAs and related therapies. Pharmacists play a vital role in ensuring these treatments lead to safe, effective and lasting improvements in health by supporting appropriate prescribing, managing side effects and helping patients achieve long-term benefit.

Dr Waseem Majeed is Consultant Endocrinologist and Clinical Lead at Salford Royal NHS Foundation Trust and Lead Consultant Endocrinologist at Oviva  

References

1. Hooper L et al. GLP-1RA-induced delays in gastrointestinal motility: Predicted effects on coadministered drug absorption by PBPK analysis. Pharmacother 2025;45(4):211-19
2. Oviva. Unpublished data set. 2025. Available on request
3. Xie Y et al. Mapping the effectiveness and risks of GLP-1 receptor agonists. Nature Med 2025;31:951-62
4. Lincoff A et al. Semaglutide and cardiovascular outcomes in obesity without diabetes. N Engl J Med 2023;389:2221-2232
5. Wolff Sagy Y et al. Glucagon-like peptide-1 receptor agonists compared with bariatric metabolic surgery and the risk of obesity-related cancer: an observational, retrospective cohort study. eClinicalMedicine 2025; 83: 103213
6. Dobbie L et al. Ten top tips for the management of GLP-1 receptor agonists in adults within primary care. Obes Facts 2025; published 19 May 2025