Start with why you want to change
People switch because of side effects, too little response, supply, cost or a different clinical goal. Each reason leads to a different decision. Severe symptoms may need investigating, and time to recover, before you start any replacement.
Tell your new prescriber the exact product, strength, last injection date, how long you have been on treatment and any missed doses. Say if a previous clinician refused or stopped treatment, and why. A receipt does not show how well you tolerate the medicine now or rule out a safety problem.
No milligram conversion works for everyone
Mounjaro contains tirzepatide, which acts on GIP and GLP-1 receptors. Wegovy contains semaglutide, a GLP-1 receptor agonist. A 5 mg dose of one does not equal 5 mg of the other. The most you tolerated on one medicine does not carry over to the next.
Moving between Ozempic and Wegovy also needs a prescribing decision, even though both contain semaglutide. The devices, licensed uses and dose schedules differ. Avoid online conversion tables. They ignore your past tolerance, any gaps in treatment and your reason for switching.
Moving between Wegovy tablets and injections
The current UK injection product information sets out one option for people on oral semaglutide 25 mg daily. They can move to the 2.4 mg weekly injection, starting the day after the last tablet. The information also warns the effect of the switch is hard to predict, because absorption from tablets varies more.
This approved switch gives no conversion table for other tablet strengths, other injection doses or anyone restarting after a long break. To move from injections to tablets, follow the tablet product information and your prescriber's instructions. Never take tablets and injections together to smooth the changeover.
Avoid overlapping by mistake
Write down the dates and confirm which prescription is ending. If supplies from two providers overlap, store the one you have stopped apart from the other and ask about returning unused medicine. Otherwise an automatic renewal leaves you unsure which plan is current.
Swapping between products in secret because one feels stronger on a given day brings no benefit. Semaglutide stays in your body for a long time. Overlapping effects raise the risk of side effects with no predictable extra gain.
Review after the switch
Your follow-up should check side effects, appetite, how much you eat and drink, and your clinical goal. If you take insulin or a sulfonylurea, you may need glucose checks and a dose review. Contraception advice also changes once tirzepatide is part of your treatment.
Ask who to contact if you cannot tolerate the new medicine or cannot get hold of it. Do not assume you can switch back by going straight onto your old high dose. Good records let your GP and dispensing pharmacy see one current plan, the reason for it and the next review date.
Sources
Your own medicine leaflet and prescriber come first. A source from another country does not mean the same rule applies in the UK.
- Wegovy FlexTouch UK prescribing information medicines.org.uk
- MHRA: advice on switching GLP-1 medicines gov.uk
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