Can You Take GLP-1 With Antibiotics? (October 2026)

01 · The core answer

Can you take antibiotics on a GLP-1 medicine?

In most cases, yes, you can be on a GLP-1 medicine and be prescribed an antibiotic, and the decision belongs with the clinician who prescribes the antibiotic. Your job is to make sure they know exactly what you inject, which strength you are on and when your last dose was. Please do not stop either medicine on your own because of something you read online.

Mounjaro (tirzepatide) is a once-weekly injectable licensed in the UK for weight management and type 2 diabetes.¹ It activates the GIP and GLP-1 receptors, which helps regulate appetite and slows how quickly the stomach empties.¹ That slowed emptying is the main reason the question comes up at all: a tablet or capsule antibiotic has to pass through the stomach first.

Check the patient information leaflet for your antibiotic and for Mounjaro, and ask a pharmacist or prescriber.¹³ If you want our fuller walkthrough for this exact pairing, see our guide on antibiotics with Mounjaro specifically.

02 · Your next step

What to do when you are prescribed antibiotics

Start by telling the person prescribing the antibiotic that you use a GLP-1 medicine, because they can only account for it if they know. This applies to a GP, an out-of-hours doctor, a dentist, a walk-in centre or a pharmacist.

• Say the brand name, the strength and that it is a weekly injection.
• Mention any other regular medicines, including oral contraception and diabetes treatments. The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.¹
• Read the antibiotic leaflet's section on other medicines and on alcohol.
• Take the antibiotic exactly as prescribed and finish the course unless a clinician tells you otherwise.
• Contact your prescribing team if you are being sick, have diarrhoea or cannot keep food and fluids down.

If you are an EverydayMeds patient, our prescribing team can talk through the effect on your treatment as part of your ongoing monthly reviews.

The decision about when to take your next injection during an infection is clinical. Ask your prescriber.

03 · Slowed stomach emptying

How slowed stomach emptying can affect oral antibiotics

Mounjaro slows how quickly the stomach empties, and that can influence how quickly an oral medicine reaches the part of the gut where it is absorbed.¹ Because of this, tell professionals about everything you take.¹³

Injectable or intravenous antibiotics, given in hospital for example, do not pass through the stomach in the same way. If you are admitted to hospital, tell the team you use a weekly injectable GLP-1 medicine and which day you take it. They need that information for any procedure and for any new prescription.

Practical tip: keep a note on your phone of your medicine name, strength and injection day. It saves time when you are unwell and someone new is reviewing your medicines.

04 · Overlapping stomach upset

Overlapping stomach upset and dehydration

Both antibiotics and GLP-1 medicines can upset the digestive system, so symptoms such as nausea or loose stools may feel stronger when you take them together. If you feel worse, contact your prescribing team.

It can be hard to tell which medicine is responsible. A sensible approach is to note when symptoms began, whether they started after the antibiotic or after an injection, and how long they last. That detail helps a clinician decide whether to change the antibiotic, adjust timing or look for another cause, including the infection itself.

Being unwell can also reduce how much you eat and drink. Because Mounjaro already makes most people feel fuller sooner,¹ a poor appetite during an infection can tip into eating too little. If you cannot keep fluids down, contact your clinical team — dehydration needs medical help straight away.

We cover that in our guide to antibiotics and appetite.

05 · Contraception and antibiotics

Oral contraception, antibiotics and Mounjaro

Mounjaro can reduce the absorption of oral contraceptives because stomach emptying slows.⁷ The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. This applies to the pill only — implants, coils and injections are unaffected.

Antibiotics add a second question. Rather than guess, check the leaflet for the pill you take and ask a pharmacist how the combination applies to you.¹³

Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly.

06 · Diabetes medicines

If you also take insulin or a sulfonylurea

If you use insulin or a sulfonylurea alongside Mounjaro, the doses of those medicines may need adjusting because of the risk of low blood sugar.¹ That is a matter for your diabetes team, and the arrival of an antibiotic is a good moment to check in with them.

Ask the pharmacist to check your antibiotic against all your diabetes medicines, and follow your team's advice on monitoring.

07 · Alcohol and antibiotics

Alcohol, flucloxacillin and other antibiotics

Whether you can drink alcohol depends on the specific antibiotic, not on Mounjaro. Some antibiotics carry an alcohol warning on the label and in the leaflet. Your pharmacist can tell you which applies to the antibiotic you have been given.

People often ask about flucloxacillin in particular. Read the leaflet in the box, and ask the pharmacist who dispenses it. Mention that you also use a weekly GLP-1 injection.

If you have accidentally had a drink while on an antibiotic, do not panic. Check the leaflet for the warning on that medicine. If it lists specific reactions and you feel unwell, seek advice from a pharmacist, NHS 111 or a doctor, and in an emergency call 999.

Alcohol adds calories that work against your goals, and drinking on a reduced appetite and emptier stomach can hit harder than usual. Our weight loss clinic pages cover day-to-day habits on treatment.

08 · Infection, exercise and recovery

Eating, activity and recovery during an infection

Mounjaro is used alongside a reduced-calorie diet and increased physical activity, not instead of them.¹ During an infection, though, your priority is to recover. That usually means resting, drinking enough and eating what you can manage, and it does not mean pushing through a hard workout. If you want ideas for returning to activity afterwards, read our page on exercising on a GLP-1 medicine.

Do not use an antibiotic course as a reason to skip meals. Appetite may already be low, so small regular portions with plenty of fluid are usually easier. If you are losing track of what you are eating or drinking, mention it to your prescriber.

If an illness is severe enough that you are considering pausing your injections, talk to the prescribing team first. Our page on whether you can take a GLP-1 medicine temporarily explains the wider picture around breaks in treatment.

09 · How long Mounjaro stays in the body

Why pausing does not remove Mounjaro quickly

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹

This matters for antibiotic questions in two ways. First, skipping one injection during a short illness does not mean the medicine has left your body, so any effect on stomach emptying does not vanish overnight. Second, if a clinician is worried about an interaction, the sensible route is to ask them, not to time your antibiotic around a guessed clearance window.

Tell anyone treating you about your most recent injection date as well as the strength. It gives them a better picture than the medicine name alone.

10 · Other weight-loss medicines

Other weight-loss medicines, retatrutide and supplements

Questions about 'what should not be taken with a GLP-1 medicine' have no single answer, because interactions depend on the product. For Mounjaro, the leaflet and SmPC are the reference documents, and a pharmacist can check your whole list of medicines against them.¹

Retatrutide is an unlicensed research peptide with no UK licence and no safety data, and Mounjaro must not be combined with it. If you have obtained any unlicensed product, tell your clinician, and report suspected side effects through the Yellow Card scheme.¹⁹

Orlistat is a different case, because it works in the gut rather than on appetite hormones. We cover it in separate guides: orlistat alongside Mounjaro and orlistat with antibiotics. Supplements marketed as natural alternatives are low-cost and have no clinical oversight, and their dosing is not standardised, so mention them to your pharmacist as well.

11 · Reporting side effects

When to get advice and how to report a reaction

Speak to a clinician if you develop a new or worrying symptom while taking an antibiotic and a GLP-1 medicine together. That includes persistent sickness, severe diarrhoea or inability to keep fluids down, which need prompt attention from your clinical team. Swelling of the face, lips, tongue or throat, or difficulty breathing, needs medical help straight away.¹³ For emergencies, call 999.

You can report a suspected side effect of any medicine through the MHRA Yellow Card scheme, and reports help regulators spot patterns.¹⁹ If you are an EverydayMeds patient, you can also contact our support team by email, through the account portal chat or by phone on 0333 207 0413, Monday to Friday, 9am to 5pm.

Mounjaro (tirzepatide) is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.

12 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹