Short answer: Mounjaro (tirzepatide) and Wegovy (semaglutide) can be taken with most everyday medicines, and the UK product information (SmPC, section 4.5) names a handful that need care. Never combine two GLP-1 medicines, and take extra care with insulin or a sulphonylurea such as gliclazide, which raise the risk of low blood sugar, and with warfarin, which needs closer INR checks when you start. Mounjaro can make the contraceptive pill less reliable for 4 weeks after starting and after each dose increase, Wegovy tablets need a 30-minute gap before any other tablet and can raise thyroxine levels in people taking levothyroxine, and the highest Foundayo dose is 9mg with medicines such as clarithromycin. Sertraline and other antidepressants, antibiotics and ADHD medicines are not listed as interactions for Mounjaro or Wegovy, and paracetamol needs no dose change.
This guide sets out what the UK product information for all four medicines, the MHRA, the NHS and the NHS Specialist Pharmacy Service say, as of October 2026, medicine by medicine. Who should not take these medicines at all is covered in our guides Is Mounjaro safe? and Is Wegovy safe? Tell us about every medicine you take: a GPhC-registered pharmacist reviews each one before anything is supplied.
What medicines can you not take with Mounjaro or Wegovy?
For Mounjaro and Wegovy, another GLP-1 medicine is the one combination to avoid outright, and Foundayo adds a few medicines to avoid. The rest is about care and checks rather than a ban, although we cannot supply anyone taking insulin or a sulphonylurea through our service. The table shows what each medicine's UK product information says, as of October 2026.
| Medicine or group | Mounjaro | Wegovy injection | Wegovy tablets | Foundayo |
|---|---|---|---|---|
| Another GLP-1 medicine, such as Ozempic | Not named in its product information. Never combined through our service | Should not be used together (4.2, 4.5) | Should not be used together (4.2) | Not named in its product information. Never combined through our service |
| Insulin or a sulphonylurea, such as gliclazide | Higher risk of low blood sugar. A lower dose of those medicines may be considered (4.2, 4.4) | Consider a lower dose of those medicines when starting (4.2) | In type 2 diabetes, consider a lower dose of those medicines when starting (4.2) | A lower dose of those medicines may be considered (4.2) |
| Metformin | The current dose can continue (4.2) | No clinically relevant change in metformin levels (4.5) | No clinically relevant change (4.5) | The current dose can continue (4.5) |
| Warfarin | Monitor, especially at the start and after each dose increase (4.5) | Frequent INR checks when starting (4.5) | Frequent INR checks when starting (4.5) | Not listed |
| The contraceptive pill | May work less well: use a non-oral or barrier method for 4 weeks after starting and after each increase (4.5) | Not expected to reduce its effect (4.5) | No clinically relevant change (4.5) | May work less well: use a non-oral or barrier method for 30 days after starting and after each increase (4.5) |
| Levothyroxine | Not listed | Not listed. The NHS lists it for semaglutide | Thyroxine exposure rose by 33%, so thyroid checks may be considered (4.5) | Not listed |
| Other tablets taken at the same time | Absorption may be slower, most of all at the start. No dose change expected for most (4.5) | No clinically relevant effect at 2.4mg. No dose change needed (4.5) | Wait at least 30 minutes. Five tablets taken together cut semaglutide absorption by 34% (4.2, 4.5) | Absorption may be slower, most of all after the first dose. No clinically relevant effect expected for commonly used medicines (4.5) |
| Strong CYP3A4 or OATP1B inhibitors, such as clarithromycin, itraconazole or ciclosporin | Not listed | Not listed | Not listed | Highest dose 9mg (4.2, 4.5) |
| Strong CYP3A4 inducers, such as rifampicin, carbamazepine, phenytoin or St John's wort | Not listed | Not listed | Not listed | Avoid: they may make Foundayo work less well (4.2, 4.5) |
| Simvastatin | Not listed | Not listed | Not listed | Your prescriber should halve the simvastatin dose (4.5) |
| Antidepressants, such as sertraline or fluoxetine | Not listed | Not listed | Not listed | Not listed. St John's wort, a herbal remedy: avoid (above) |
| Antibiotics | Not listed | Not listed | Not listed | Clarithromycin: highest dose 9mg. Rifampicin: avoid (4.5) |
Source: the UK Summaries of Product Characteristics on the electronic medicines compendium, sections 4.2 and 4.5: Mounjaro KwikPen (emc 15481, revised 29 August 2026), Wegovy FlexTouch (13803, revised September 2026), Wegovy tablets (102344, revised June 2026) and Foundayo (102527, revised 10 August 2026), read October 2026. "Not listed" means the product information names no interaction, not that none can ever happen, which is why your pharmacist reviews every medicine you take.
List everything. In your consultation, list every medicine you take: prescribed, bought without a prescription, herbal remedies and supplements.
A pharmacist reviews it. A GPhC-registered pharmacist reviews every medicine you list before anything is supplied, and may ask you more about it.
Keep taking your medicines. Keep taking them as prescribed unless your prescriber tells you otherwise. Never stop or change one to start weight loss treatment.
Tell us about anything new. If a doctor, dentist or pharmacist starts you on something new, tell them you take a GLP-1 medicine, and tell us at your next reorder.
Why do weight loss injections affect other medicines?
Mainly because they can slow how quickly your stomach empties, which can change how fast tablets are absorbed. The Mounjaro product information says tirzepatide delays stomach emptying, that the effect is strongest when you start treatment, and that no dose change is expected for most medicines taken by mouth (SmPC 4.5). For semaglutide, the Wegovy product information reports no clinically relevant effect on the rate of stomach emptying at the 2.4mg dose, and no dose change for other medicines (SmPC 4.5).
Two kinds of medicine need more thought: those where small changes in level matter (a narrow therapeutic index, such as warfarin and digoxin, which the Mounjaro product information asks to be monitored), and those that must work quickly or at set times. The NHS Specialist Pharmacy Service (SPS) advises caution with time-critical medicines such as levodopa for Parkinson's disease, while noting that in most cases the manufacturers' studies have not shown clinically relevant interactions.
Can you take diabetes medicines with Mounjaro or Wegovy?
Metformin can be continued, but insulin and sulphonylureas need care, because together with a GLP-1 medicine they raise the risk of low blood sugar. The product information for all four medicines says a lower dose of insulin or a sulphonylurea may be considered when treatment starts. GLP-1 treatment with insulin or a sulphonylurea can cause dangerously low blood sugar (hypoglycaemia). This needs to be managed by your GP or diabetes team, who can adjust your existing medicines at the same time.
For that reason we cannot supply weight loss treatment through our service to anyone taking insulin or a sulphonylurea (sulphonylureas include gliclazide, glimepiride, glibenclamide and tolbutamide). Where a diabetes team does lower insulin, SPS advises doing it step by step, because the MHRA has had reports of diabetic ketoacidosis in people with type 2 diabetes whose insulin was cut quickly or stopped.
With Mounjaro or Foundayo, the current dose of metformin or an SGLT2 inhibitor can continue (Mounjaro SmPC 4.2, Foundayo SmPC 4.5), and semaglutide did not change metformin levels to a clinically relevant degree (Wegovy SmPC 4.5). The NHS still lists diabetes medicines among those to mention before you start. More is in our guide to Mounjaro and type 2 diabetes.
Does Mounjaro or Wegovy affect the contraceptive pill or HRT?
Mounjaro and Foundayo can make the contraceptive pill less reliable for a while; Wegovy injections and Wegovy tablets are not expected to. The MHRA repeated the Mounjaro advice in June 2025, when it reminded women on these medicines to use effective contraception. This is the counselling we give every patient:
Mounjaro and Wegovy injections: Contraception (Mounjaro only): tirzepatide can reduce absorption of the contraceptive pill. Use a non-oral method or add condoms for 4 weeks after starting and for 4 weeks after each dose increase. Wegovy needs no extra precautions unless severe vomiting or diarrhoea occurs, then follow missed-pill guidance.
Foundayo: If you use the oral contraceptive pill, use a non-oral method or add a barrier method such as condoms for 30 days after starting treatment and for 30 days after each dose increase.
For Wegovy tablets, the product information found no clinically relevant change in the levels of a pill containing ethinylestradiol and levonorgestrel (SmPC 4.5). Methods not taken by mouth, such as patches, rings and implants, need no extra barrier method, SPS says. Medicine by medicine, including pregnancy, is in our guide to contraception and pregnancy on GLP-1 treatment.
HRT taken through the skin is not affected by GLP-1 medicines, according to SPS, which also says prescribers can consider moving women on HRT tablets who start a GLP-1 medicine to HRT through the skin. Talk to whoever prescribes your HRT rather than changing it yourself. Our guide to Mounjaro and HRT has more.
Can you take warfarin with Mounjaro or Wegovy?
Yes, but your INR, the blood test that checks warfarin, should be watched more closely when you start. The Wegovy injection and tablet product information recommends frequent INR checks when semaglutide is started in people on warfarin or a similar coumarin, because lower INR readings have been reported with acenocoumarol (SmPC 4.5). The Mounjaro product information asks for monitoring of warfarin and digoxin, especially at the start and after each dose increase (SmPC 4.5). Foundayo's product information does not list warfarin. Keep taking warfarin as prescribed, and tell the clinic that manages it before you start.
Our consultation asks whether you take warfarin, digoxin, lithium, levothyroxine, an immunosuppressant or an antiepileptic. None of these on its own stops you having treatment: a GPhC-registered pharmacist reviews your answer and may ask you more before anything is supplied.
Can you take levothyroxine with Mounjaro or Wegovy?
Yes. Levothyroxine is not listed as an interaction in the product information for Mounjaro or Wegovy injections, although the NHS lists it among the medicines to mention before you use semaglutide. Wegovy tablets are the exception to know about: in a study, the body's exposure to thyroxine rose by 33% after a dose of levothyroxine, so the product information says thyroid blood tests should be considered (SmPC 4.5).
If you take both tablets in the morning, the Wegovy tablet comes first, on an empty stomach, and you wait at least 30 minutes before taking levothyroxine, as with any other tablet. Your pharmacist can help you plan the timing. Keep taking levothyroxine as prescribed, and tell your GP you have started a weight loss medicine.
Can you take antidepressants such as sertraline with Mounjaro or Wegovy?
Yes: no antidepressant, sertraline and fluoxetine included, is listed as an interaction in the UK product information for Mounjaro, Wegovy injections, Wegovy tablets or Foundayo, and taking one does not on its own stop you having treatment through our service. As with any tablet, slower stomach emptying can change how quickly it is absorbed, most of all when you start Mounjaro, so tell your pharmacist. Lithium is different: our consultation asks about it, because small changes in its level matter.
Keep taking your antidepressant as prescribed. In October 2026 the MHRA announced a new boxed warning for antidepressant leaflets about suicidal thoughts and behaviours. It says these are not new risks, that you should get urgent help if you have new or worsening suicidal thoughts, particularly when starting an antidepressant or changing its dose, and that you should not stop the medicine without speaking to your healthcare professional. On GLP-1 medicines themselves, SPS reports that the MHRA found no evidence of a causal link with suicidal thoughts, self-harm or depression. If you have thoughts of harming yourself, get help straight away. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time. The evidence is in our guide to whether Mounjaro can cause depression.
Can you take antibiotics, painkillers or ADHD medicines with Mounjaro or Wegovy?
Yes: no antibiotic or ADHD medicine is listed as an interaction for Mounjaro, Wegovy injections or Wegovy tablets, and paracetamol, the one painkiller the Mounjaro product information mentions, needs no dose change. Foundayo has two exceptions among antibiotics: with clarithromycin the highest Foundayo dose is 9mg, and rifampicin should be avoided (SmPC 4.5). With an infection, the illness can matter more than the antibiotic: vomiting or diarrhoea can dehydrate you, so keep sipping fluids.
A single 5mg dose of Mounjaro halved paracetamol's peak level and delayed it by about an hour, but after four weekly doses there was no effect (SmPC 4.5), so in the first weeks a painkiller may take a little longer to work. Ibuprofen is not listed, but the NHS advises anyone with indigestion, which these medicines can cause, not to take ibuprofen or aspirin unless prescribed, because both can make it worse. ADHD medicines such as methylphenidate and lisdexamfetamine are not named in the product information of any of the four medicines; list them in your consultation, as with every other medicine.
Taking other medicines and wondering whether weight loss treatment is suitable? Our consultation asks about every medicine you take, and a GPhC-registered pharmacist reviews each one before anything is supplied.
Check your eligibilityHow do you take other medicines with the Wegovy pill?
Take the Wegovy tablet first, on its own, and wait at least 30 minutes before any other tablet, food or drink. This is the counselling every Wegovy tablets patient receives from us:
One tablet, once a day. Timing is everything. Take your tablet on an empty stomach after fasting for at least 8 hours (for most people, first thing in the morning). Swallow it whole with up to 120 ml of water. Don't split, crush or chew it. Then wait at least 30 minutes before any food, drink, or other medicines taken by mouth. The 30-minute wait includes water beyond the small amount you take the tablet with, and yes, that includes your morning tea or coffee. Eating or drinking sooner significantly reduces how much medicine your body absorbs, which means it simply won't work as well.
Other tablets matter because semaglutide tablets are absorbed from the stomach. In a study in the product information, taking a Wegovy tablet together with five other tablets left the body's exposure to semaglutide 34% lower, and its peak level 32% lower (SmPC 4.5). Omeprazole made no clinically relevant difference to semaglutide's absorption. The full routine is in our guide to how to take the Wegovy pill.
Which medicines change the Foundayo dose?
A few can. If you take ketoconazole, itraconazole or clarithromycin, or ciclosporin, the UK product information sets the highest Foundayo dose at 9mg once daily, because these medicines raise the amount of Foundayo in your blood. Others, including St John's wort, can make Foundayo work less well.
The product information says to avoid strong CYP3A4 inducers, such as rifampicin, phenytoin, carbamazepine and St John's wort, because they lower the amount of Foundayo in the blood. Medicines that strongly block both CYP3A4 and OATP1B, such as the HIV medicine ritonavir, should be avoided altogether (SmPC 4.2 and 4.5). Foundayo can be taken at any time of day, without food or water restrictions, so it carries no 30-minute rule. Each step is in our guide to how to take Foundayo.
Can you take vitamins, supplements or herbal remedies with Mounjaro or Wegovy?
Usually, yes: no vitamin is listed as an interaction in the UK product information for Mounjaro, Wegovy injections or Wegovy tablets, and the one herbal remedy named for any of the four medicines is St John's wort, which should be avoided with Foundayo. The NHS advises telling your doctor or pharmacist about any herbal remedies, vitamins or supplements before you start, so list them in your consultation. With Wegovy tablets, a vitamin or supplement is something taken by mouth, so take it after the 30-minute wait. More is in our guide to vitamins and supplements on Mounjaro and Wegovy.
Can you take another weight loss medicine at the same time?
No. Weight-loss medicines are not taken together through our service, and our pharmacist confirms with you that an earlier one has stopped before anything is supplied. The Wegovy injection and tablet product information says semaglutide should not be used with any other GLP-1 medicine, and our consultation also asks about orlistat, Alli and slimming supplements. How orlistat compares is in our guide to orlistat vs Mounjaro.
Moving from one medicine to another is a switch, not a combination, and SPS notes there is very little data on how to switch, so it is planned with a pharmacist or doctor. Our guide to switching between Mounjaro and Wegovy explains how a switch works.
Do you need to stop Mounjaro or Wegovy before an operation?
Keep taking it unless your surgical or anaesthetic team tells you otherwise, but tell them you take it before any operation or dental procedure that needs a general anaesthetic or sedation. This is the advice we give every patient:
Before any operation: tell your surgical or anaesthetic team you take a GLP-1 medicine. It slows stomach emptying, which matters for anaesthesia.
Keep taking the medicine you already have as usual, unless your surgical or anaesthetic team tells you otherwise.
The MHRA explained the reason in January 2025: with a slower-emptying stomach, food and drink can still be in your stomach after the usual fasting time, and during a general anaesthetic or deep sedation it could reach your lungs. The product information for each of the four medicines carries the same warning, and the NHS lists an anaesthetic or a sedative for an operation or dental procedure among the things to tell the healthcare professional about. Report any suspected side effect on the MHRA Yellow Card website.