Weight loss HGH injections: what the evidence actually says

What is HGH, and does it actually work for weight loss?

Human growth hormone, produced naturally by the pituitary gland, plays a role in body composition throughout life. Levels tend to fall with age, and that decline is associated with a modest shift towards greater fat mass and less lean tissue. That biological fact is the foundation of a lot of marketing around HGH injections for weight loss, but the marketing goes considerably further than the evidence does.

In adults who have a genuine growth hormone deficiency diagnosed through specialist endocrine assessment, HGH therapy is prescribed on the NHS and can improve body composition as part of a broader treatment plan. That is a specific, narrowly defined medical condition. The licensed use does not extend to adults who simply want to lose weight or who have age-related reductions in growth hormone within the normal range.

The clinical studies that have looked at HGH in adults without true deficiency generally show modest changes in body composition (some loss of fat mass, some gain in lean mass) but not meaningful or sustained weight reduction as such. Side effects at supraphysiological doses can be significant, including fluid retention, joint pain, carpal tunnel symptoms, and an increased risk of insulin resistance. The NHS guidance on obesity treatment does not include HGH as a weight-management option for the general adult population.

It is also worth checking any product described as an HGH injection against the MHRA's guidance on verified UK pharmacy sources, because if you are exploring safer and properly licensed alternatives, our page on weight loss injections explains which options are legally available and how they work.

Which injectable medicines are actually licensed for weight loss in the UK?

Two injectable medicines hold UK marketing authorisations specifically for weight management in adults: tirzepatide, sold as Mounjaro, and semaglutide, sold as Wegovy. Both are once-weekly subcutaneous injections. Both are prescription-only medicines, meaning they can only be supplied legally after a prescriber has assessed whether they are clinically appropriate for you.

Tirzepatide works on two gut-hormone receptors simultaneously (GIP and GLP-1), which distinguishes it from every other licensed weight-loss injection currently available. In the SURMOUNT-1 trial, published in the New England Journal of Medicine, participants on the highest dose lost an average of around 20–21% of their body weight over 72 weeks. Semaglutide, a GLP-1 receptor agonist, produced around 15% average reduction over 68 weeks in the STEP 1 trial. These figures come from thousands of adults in randomised controlled trials; they are the most credible numbers available, and they are for licensed, clinically supervised treatment.

If you are weighing up the two options, our page on the main injectable options available in the UK sets out how they compare in plain terms. The right choice depends on your health history and clinical circumstances, which is exactly what a prescriber assesses.

Eligibility for the licensed treatments broadly covers adults with a BMI of 30 or above, or 27 or above if a weight-related health condition is present. Lower thresholds apply for some ethnic backgrounds under UK guidance. BMI alone never guarantees a prescription; the prescriber looks at the full picture.

Why are unlicensed HGH injections sold online a problem?

The short answer is that they sit outside any meaningful safety framework. The MHRA has been clear, and increasingly active, about the risks of weight-loss injectables sold online without proper clinical oversight. In 2025 the agency seized approximately 20 million doses of illegally traded weight-loss medicines with an estimated street value of around £45 million, including the first UK raid on an illicit manufacturing site producing counterfeit tirzepatide pens. Fake pens have been found to contain entirely wrong substances, including insulin in some cases, which can cause life-threatening hypoglycaemia.

This risk applies to any injectable claiming weight-loss effects that is sold outside the licensed UK supply chain, whether labelled as HGH, GLP-1, peptides, or anything else. The MHRA's Yellow Card scheme allows anyone to report a suspect seller or a product they are concerned about; it is a practical tool and takes under a minute to use.

Sellers that offer these products freely, with no clinical assessment required, are operating outside UK law. For a prescription medicine, the price or speed of access is not the right measure of value; the clinical oversight and verified supply chain are. Our page on what to think about before prioritising price with weight-loss injections covers this in more depth.

How does a legitimate consultation for a licensed injectable work?

For people who have been searching for HGH-based approaches but are now considering the licensed GLP-1 route, the process through a regulated UK pharmacy is straightforward. A GPhC-registered Independent Prescriber reads your consultation, verifies your identity and your weight, checks your medical history, and makes a clinical decision. It is a real person reviewing your case, not automated software. You can verify any online pharmacy you are considering on the GPhC register before you share any personal or health information with them.

At nume, consultations are reviewed the same day by a GPhC-registered prescriber. Orders placed before 12pm on a working day are dispatched the same day once approved, and arrive free the next working day via tracked DPD delivery, in plain packaging. There are no subscription traps and no hidden fees. Our clinical and pharmacy team is available to answer questions before and after you start treatment.

If you have existing concerns about how your body is responding to any injectable treatment, or if you experienced side effects from something you obtained elsewhere, our page on the side effects of weight-loss injections gives a clear account of what is known, and when to seek medical help promptly.

Ready to find out whether a licensed treatment is right for you? If you are based in the area, you can also read about weight loss injections available in Newry and how local access works. Start your free consultation and a prescriber will be in touch the same day.