How much water do you add to semaglutide — and why that question matters

Does licensed semaglutide in the UK need water added to it?

No. Both forms of licensed semaglutide available in the UK come prepared. Wegovy as a weekly injection is a pre-filled pen, you click the cap, press against the skin, and inject. There is no vial, no powder, no syringe, and no water involved. The NHS semaglutide medicine guide describes it as a subcutaneous injection given once a week, with the dose already loaded in the device.

The oral version, Wegovy tablets, approved by the MHRA in June 2026, is simpler still: a tablet taken first thing in the morning with a small sip of plain water, nothing else added or measured.

So if a product you're looking at online requires you to figure out how much water to mix with semaglutide, that product is not licensed Wegovy. It is likely a compounded preparation, manufactured outside the licensed supply chain, with no MHRA oversight of its potency, sterility or safety. The reconstitution step is the tell.

A quick check takes under a minute: go to the GPhC pharmacy register, enter the name or registration number of whoever is selling to you, and confirm they appear as a registered pharmacy. If they don't, stop there.

Why are some sites asking you about water quantities, then?

Compounded semaglutide (typically a lyophilised (freeze-dried) powder in a vial) became widespread during Wegovy shortages. Sellers, often operating outside UK pharmacy regulation, supplied it alongside bacteriostatic water and instructions for home reconstitution. If you've come across guidance on how much water to add to 5mg semaglutide, that is a direct product of that unregulated market, not something that applies to licensed treatment.

The MHRA has been explicit about the risks. Fake and unlicensed weight-loss pens have been seized in large volumes across the UK, enforcement in 2025 alone involved roughly 20 million doses of illegally traded medicines worth around £45 million, including the first UK raid on a site manufacturing counterfeit tirzepatide pens. Some seized products contained insulin rather than semaglutide, with serious consequences for the people who used them.

Getting the reconstitution volume wrong adds another layer of risk on top of an already unsafe product: an overdose or an underdose of an unverified substance, administered by someone who has not been trained to reconstitute injectables. None of that risk exists with a licensed pre-filled pen from a regulated pharmacy. If you are trying to work out how much water to mix with 5mg semaglutide, that question itself is a signal that the product in front of you sits outside the licensed supply chain.

For background on bacteriostatic water and semaglutide, the short answer is that this combination has no place in legitimate licensed weight-loss treatment in the UK.

What does properly priced licensed semaglutide actually cost?

Private Wegovy prices in the UK vary by dose and provider, and our Wegovy stock price page covers how availability and competitive dynamics have shifted the cost picture recently. Since Eli Lilly raised Mounjaro's list price sharply from September 2025 (a move that shifted competitive dynamics across the whole GLP-1 market) semaglutide has remained the price-accessible alternative for many patients, with private monthly costs typically reported somewhere in the range of £149 to £375 depending on dose and the clinic involved. Those figures are widely referenced but hedged: your actual cost will depend on which dose you're prescribed and which provider you use.

What those headline numbers often don't include is worth knowing: some providers charge separately for the consultation, the prescription, and delivery. Aftercare (the clinical support you need when a side effect appears or a dose change is due) is sometimes an add-on or simply absent.

At nume, one price covers the consultation, the prescription, the medicine, free next-working-day DPD delivery, and seven-day aftercare. We are not the cheapest option available online; that is a deliberate choice, not an oversight. Current treatment pricing is on our Wegovy price page, and our consultation page is where to begin if you want a prescriber to assess your suitability.

Is 'cheapest' even the right question for a prescription medicine?

For most purchases, price is a sensible filter. For a Prescription-Only Medicine injected subcutaneously once a week, it isn't. The relevant questions are: is this product licensed by the MHRA? Is the pharmacy registered with the GPhC? Was a qualified prescriber involved, not a checkbox form, but a clinician who has seen evidence of your weight, reviewed your medical history, and made a professional judgement?

A low price from an unverified source can mean a product that requires reconstitution, carries unknown potency, and arrives with no clinical oversight attached. The MHRA's Yellow Card scheme exists partly to capture adverse events from exactly these situations, and you can use it to report a suspect seller as well as a suspected side effect.

On Wegovy specifically, the full treatment overview covers what the licensed schedule looks like, what results the clinical trials showed, and how eligibility is assessed. Hydration during treatment is a separate, genuinely useful topic, if you're wondering how much water to drink on semaglutide, that guidance is there too. Treatment that keeps you safe costs more than a vial of unverified powder. That's not a marketing line; it's just how regulated medicine works.