Prescription vs Over‑the‑Counter Weight Loss Drugs

Some weight loss medicines need a prescription from a doctor, while others can be bought in pharmacies or online. Prescription treatments are usually stronger and require medical supervision. Over-the-counter (OTC) products are milder but can still have side effects or interactions.

Prescription medicines are licensed for specific medical conditions such as obesity or type 2 diabetes. They have been tested in large clinical trials and are monitored by regulators like the MHRA and EMA.
Over-the-counter medicines and supplements vary widely. Some contain clinically tested ingredients, such as orlistat (Alli), while others rely on herbal or unproven compounds. Choosing safely depends on your health profile, medications, and goals.

Prescription medicines are stronger, require a doctor’s assessment, and have proven results. OTC products are easier to get but often less effective.

• Prescription medicines: contain higher doses, require safety checks, and come with clear dosing instructions and monitoring plans.
• OTC options: available in pharmacies and online, often lower strength or unlicensed as medical products.
• Regulation: prescription products are MHRA-licensed medicines; many OTC supplements are regulated as food or cosmetics, not drugs.

Prescription GLP-1 and dual agonist medications usually produce much greater average weight loss than OTC products.

• GLP-1 receptor agonists (e.g., semaglutide) reduce body weight by about 10–15% on average over 12–18 months.
• Dual GIP/GLP-1 agonists (e.g., tirzepatide) show up to 22% average loss.
• Orlistat (OTC version) typically leads to 3–5% weight reduction if taken correctly.
• Supplements and herbal products rarely produce clinically meaningful changes.

All weight loss medicines can cause side effects. Prescription drugs are carefully studied, but OTC products can vary and sometimes interact with other medicines.

• Prescription GLP-1s: nausea, constipation, reflux, and fatigue early on.
• Orlistat: oily stools, urgency, flatulence, and reduced absorption of fat-soluble vitamins.
• Supplements: unverified ingredients may cause jitteriness, diarrhoea, or liver strain.
• Always check with a pharmacist or doctor before combining treatments.

Prescription medicines are more expensive and may not always be covered by the NHS. OTC products are cheaper but less effective.

• Private GLP-1s: £150–£300 per month, depending on brand and dose.
• Orlistat (Alli): £30–£50 per month from pharmacies.

Supplements: wide variation, often £10–£60 per month.
Cheaper doesn’t mean safer or better. Medicines with proven benefits cost more because they’ve been clinically validated.

Always base your choice on professional advice and trusted brands. Avoid unlicensed or imported medicines sold without proper verification.

• Look for MHRA-approved products.
• Avoid unregulated “fat-burning” or “detox” pills online.
• Seek professional review if you have diabetes, high blood pressure, or take other medicines.
• Combine medication with structured lifestyle support for lasting results.

Dr Abby Hyams completed her medical training in Bristol and has been a GP for 19 years, spending many of those as a partner in an NHS practice in Hemel Hempstead. She has a particular passion for supporting patients with weight loss and promoting positive behaviour change, helping individuals build sustainable habits that improve their long-term health and wellbeing.

This article is for general information only and should not be used for the diagnosis or treatment of medical conditions. Medic Spot Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. In the event of an emergency, please call 999 for immediate assistance.

There is no guarantee of a specific weight loss medication being prescribed. Clinicians will review your online questionnaire alongside other independently validated medical information about you and will recommend the most appropriate weight loss treatments for you based on your answers. In some cases, the clinicians may contact you for additional information. See Terms of Service for more information.