Practical Guide · UK Private & NHS Routes
How to get weight loss injections in the UK
From checking whether you qualify, to what happens on the day your pen arrives. Four phases — most people go from first enquiry to first injection in two to four weeks.
Check your eligibility
Weight loss injections are prescription-only medicines. Before anything else, you need to meet clinical criteria — set by the medicines regulator and the prescribing guidelines clinicians follow. The main criteria are BMI and the presence of at least one weight-related health condition, though the exact thresholds vary slightly by medication.
NHS route
Referral is via your GP. Criteria for Wegovy (semaglutide) on the NHS: BMI ≥ 35 plus one weight-related condition, or BMI 30–34.9 in certain high-risk groups. Access is currently limited to specialist weight management services and is being rolled out in phases.
Mounjaro (tirzepatide) is not currently commissioned on the NHS for weight management outside of clinical trials.
Private route
Online private clinics and pharmacies prescribe to their own clinical criteria, which generally mirror NICE guidance. Most require: BMI ≥ 30 (or ≥ 27 with a weight-related condition such as pre-diabetes, hypertension, or high cholesterol). No GP referral is needed.
This is the route most people using PenCompare are taking. Costs vary significantly between providers — that is what our comparison table is for.
Not sure if you qualify? Our eligibility checker works through the standard BMI and condition criteria for each medication.
The consultation
With a private provider, the consultation typically happens online — either a live video call with a clinician, or a detailed medical questionnaire reviewed by a prescriber. Both routes are legitimate if the provider is GPhC-registered and a qualified prescriber reviews your information before any prescription is issued.
What the consultation covers: your current weight and height, relevant medical history (type 2 diabetes, heart disease, thyroid conditions), current medications and any contraindications, previous weight management attempts, and what you are trying to achieve.
What a legitimate consultation will not do: it will not skip contraindication screening, it will not let you select your own dose, and it will not let you reach a prescription-only medicine without a clinician seeing your information first.
If a site lets you add a prescription medicine to a basket without any consultation, leave it. That is not a faster service — it is an unregistered seller operating outside the law.
Prescription and dispensing
Once a prescriber approves your consultation, the prescription is sent to a registered pharmacy for dispensing. With most online private providers, this happens within the same platform — you do not need to take a paper prescription anywhere.
Most providers dispense a single month’s supply initially, at the starting dose, before subsequent supplies at updated doses as you titrate. A few offer multi-month bundles — these are only economical if your dose stays stable, which is unlikely in the first few months of treatment.
Delivery is typically next-day in refrigerated packaging. The pen must stay refrigerated until first use, and can then be kept at room temperature for a defined period per the patient information leaflet.
Before you pay: prices between providers for the same medication and dose can differ by £80–£150 per month. The PenCompare tables show standard listed prices — no promotional pricing included — so comparisons are like-for-like.
Starting treatment
Both Mounjaro and Wegovy are injected once weekly, subcutaneously — into the skin on the abdomen, thigh, or upper arm. Both come in pre-filled auto-injector pens designed for self-administration. Your provider should supply injection technique guidance alongside the prescription; most also offer a nurse helpline.
Both medications begin at a low starting dose and step up every four weeks during a titration period. This is deliberate — slower titration reduces gastrointestinal side effects. Do not self-escalate your dose ahead of your prescriber’s schedule.
Most private providers include follow-up check-ins at regular intervals. These are clinical contacts, not sales calls — use them to report side effects, discuss dose progression, or raise any concerns about the medication.
When your pen arrives, run through the medication safety checklist before your first injection — it takes three minutes and covers the pharmacy, the package, and the pen itself.
Next steps
Once you know which medication fits your situation, the comparison tables will show you what each verified provider charges for the same pen at the same dose.