How Much Bacteriostatic Water to Mix with 10mg of Semaglutide — and Why the Question Itself Is a Red Flag

You've found a powder and a vial. Here's what that tells you about the seller.

Picture the scenario: you've come across an online listing (perhaps on social media, perhaps through a forum) offering "10mg semaglutide" as a powder that you reconstitute yourself by adding bacteriostatic water. The listing may even include a mixing guide, a dosing calculator or reassuring-sounding language about purity. It looks professional enough.

The problem is structural. In the UK, semaglutide for weight management exists in exactly two licensed forms: Wegovy injection (pre-filled pen, ready to use) and Wegovy tablets (oral, swallowed whole, no mixing involved). The MHRA, which licenses medicines in the UK, has not authorised any powdered semaglutide product for reconstitution for weight loss purposes. Questions like how much bacteriostatic water to mix with 5mg of semaglutide are therefore not practical questions for anyone accessing treatment through a legitimate UK route, they simply don't come up.

The MHRA warned publicly from October 2023 onwards about fake and illegally traded weight-loss pens, and by 2025 enforcement had uncovered approximately 20 million doses of illegally traded weight-loss medicines worth around £45 million, including, crucially, the first UK site manufacturing counterfeit tirzepatide pens. Fake pens have been found to contain insulin rather than the labelled product, with serious consequences for some users. You can report a suspect seller at the MHRA's Yellow Card scheme.

What private Wegovy actually costs, and what that price includes

Private semaglutide treatment in the UK is priced per pen or per month and varies between providers. Since Eli Lilly's list-price changes in September 2025 reshaped the broader injectable weight-loss market, typical private Wegovy prices have broadly ranged from around £149 to £375 per month depending on dose and provider, these are widely reported figures, and your own quote will depend on which dose you're prescribed and where you go.

That range matters because headline prices from different providers often exclude things that add up: a separate consultation fee, a prescription charge, a delivery fee on each order, or an ongoing subscription that auto-renews without a clinical review. If you want to understand how much water to mix with 5mg semaglutide, that is a question that only arises with unlicensed powder products, not with any legitimately prescribed Wegovy pen, so the advertised entry price doesn't reflect what you'd pay once titrated upward.

You can see what's included in a nume prescription on the Wegovy price page. For context on how the broader treatment landscape works, our weight-loss overview explains the options side by side.

One thing to be straightforward about: we are not the cheapest option you'll find. That's a deliberate choice. A single price at nume covers the consultation, the prescription, the medicine and free next-working-day delivery, tracked by DPD, in plain unbranded packaging. Nothing hidden, nothing on auto-renew. Every repeat order gets a fresh clinical review before anything ships.

Why "cheapest" is the wrong question when you're buying a prescription medicine

For most purchases, price is a perfectly sensible primary filter. For a prescription-only medicine, it isn't, and the reconstitution question is the clearest illustration of why.

A lower price on a powder-plus-vial product reflects the fact that it has bypassed the licensed supply chain entirely. There's no prescriber, no regulated pharmacy, no MHRA oversight of what's actually in the vial. The questions our prescribers hear most often include variants of "is this product safe if it's the right molecule?" The honest answer is: without verified manufacturing standards and a cold chain you can trace, you can't know what concentration you're injecting, what's in the excipients, or whether the dose on the label bears any relationship to the dose in the pen.

Any online pharmacy dispensing licensed semaglutide in the UK must be registered with the GPhC. You can verify a pharmacy's registration at the GPhC pharmacy register. If a seller cannot be found there, or offers you medicines without a prescription from a registered prescriber, walk away. The MHRA's guidance on GLP-1 medicines (available on GOV.UK) is unambiguous on this point.

The NHS overview of semaglutide on the NHS medicines pages describes how this medicine works and what the legitimate forms look like, a useful cross-reference if you've been presented with something unfamiliar.

The regulated route, what eligibility actually looks like at a UK pharmacy

Wegovy injection is licensed for adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related condition such as high blood pressure, raised cholesterol or type 2 diabetes. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. Tablets follow the same broad framework. A prescriber assesses the full picture (medical history, current medicines, any contraindications) before anything is prescribed. BMI alone doesn't settle it.

At nume, that assessment is carried out by a GPhC-registered Independent Prescriber the same day you submit your consultation. If you're curious about how much bacteriostatic water to mix with semaglutide, it is worth knowing that this question applies only to unlicensed reconstituted powders, not to the pre-filled Wegovy pens dispensed through regulated UK pharmacies. Details about how the consultation works are on our about page, and our clinical team page explains who reviews your case.

Patients sometimes ask how much semaglutide lowers blood sugar, which is a relevant consideration for anyone with type 2 diabetes or raised glucose levels who is being assessed for Wegovy. If you're ready to find out whether Wegovy is right for you, the starting point is a free consultation. There's no obligation, no subscription, and no auto-renewal, just a clinical assessment by a real prescriber.

Speak to our prescribers and start your free consultation.