Your Monday weight loss injection: what happens on injection day

Monday morning arrives, here is what the next few minutes actually look like

Picture it: it is Monday, the pen has been sitting in the fridge since it arrived. You take it out about 30 minutes before you plan to inject, because injecting cold medicine straight from the fridge can sting more than room-temperature liquid does. While it sits on the counter, you wash your hands thoroughly. You tear open an alcohol swab, clean the patch of skin you have chosen (most people use their abdomen to begin with) and let it dry completely before touching the area again.

You pick up the pen, remove the cap, press the pen gently to your skin, and activate it. The injection itself takes only a few seconds. After removing the pen, apply light pressure with a clean finger; there is no need to rub. The used pen goes straight into a sharps container, household bins are not safe for needles. That is the mechanical part done.

What you should not do: reuse the needle, inject into skin that looks sore, bruised or hardened, or inject into the same spot two weeks running. The NHS medicines page for tirzepatide covers injection technique in plain language if you want a step-by-step reference alongside your Patient Information Leaflet.

The 24–48 hours after your Monday injection

For many people, the hours after an injection are uneventful, especially once they are several weeks into treatment. At the start, or after a dose increase, Monday afternoon and Tuesday can involve some nausea, loose stools, tiredness, or a general sense of not wanting to eat much. This is the body adjusting to the medicine slowing gastric emptying and signalling fullness more strongly than usual.

There is an honest acknowledgement worth making here: the first few Mondays can feel discouraging. Nausea on a working day is not fun, and it is tempting to wonder whether it is worth it. Most people find that these effects settle significantly over the first four to six weeks, and many report they become barely noticeable by the time they reach a higher dose in the titration schedule. Staying well hydrated matters; large, fatty meals close to injection time tend to make nausea worse. Small, plain meals are easier on Mondays and Tuesdays while your system adapts.

A smaller group of people experience injection-site redness or mild itching for a day or two. Rotating sites (abdomen one Monday, thigh the next) significantly reduces this. If you develop severe or persistent abdominal pain that spreads towards your back, seek urgent medical attention; this can be a sign of pancreatitis, which the MHRA highlighted as an infrequent but serious side effect in a January 2026 Drug Safety Update. You can also report any suspected side effects at the MHRA's Yellow Card scheme.

Staying on schedule: missed days, holidays and what to do

Life intervenes. Sometimes Monday passes without the injection being taken, you were travelling, you forgot, the pen was not to hand. The general principle for once-weekly medicines is that a missed dose can usually be taken within a few days of the scheduled day, as long as the next dose is not due within a short window. For the exact guidance on what to do in your specific situation, the rule is simple: your Patient Information Leaflet and your prescriber are the authorities, not a general webpage. Do not double up doses.

If you are thinking about changing your injection day (say, moving from Monday to Wednesday to fit around a holiday) this is usually possible as long as the doses remain at least a few days apart. Again, your prescriber can confirm the right approach for your treatment. You can explore how weekly weight loss injections work more broadly if you want background on either medicine before speaking with our team.

For context on what a full month of treatment involves, including how titration typically progresses, our page on weight loss injections after the first month is a useful next step. And if you are weighing up the financial side of treatment, a clear overview of what weight loss injections cost in the UK explains what to look for and what should always be included in any quoted price.

Eligibility and starting treatment on a regular weekly schedule

Both Mounjaro and Wegovy are licensed for adults with a BMI of 30 or above, or 27 and above alongside at least one weight-related condition such as high blood pressure, raised cholesterol, type 2 diabetes or obstructive sleep apnoea. Lower BMI thresholds may apply for some ethnic backgrounds under UK guidance. A BMI figure alone is not the whole picture, the prescriber assesses your full health history before approving treatment.

At nume, every consultation is read by a GPhC-registered Independent Prescriber, not a piece of software. Identity is verified by photo ID, weight is confirmed on a live video call, and if treatment is approved before midday Monday to Friday, it leaves our pharmacy the same day with free next-working-day tracked delivery through DPD. There are no subscription traps; every repeat order is clinically re-reviewed. If you want to understand more about the clinical team behind that process, our clinical lead's profile is there to read. You can also look at the full range of weight management treatments we offer, including our Monzo weight loss injection, our weight loss injection options, and the range of weight loss injection r treatments available, before deciding what to ask about in your consultation.