What medicines can you not take with Mounjaro?

Mounjaro (tirzepatide) is a weekly injection used for weight loss and type 2 diabetes. Because it slows how quickly your stomach empties, it can affect how some medicines are absorbed, and it overlaps with treatments that lower blood sugar.

Most interactions aren't dangerous, but some medications need closer monitoring than a remote service like Voy can offer. The table below shows whether each medication is safe with Mounjaro clinically, and whether Voy can prescribe alongside it.

Who shouldn't take Mounjaro? (Mounjaro contraindications)

Mounjaro isn't suitable for everyone. Voy can't prescribe Mounjaro if you:

• Are under 18 years old
• Are trying to conceive, pregnant, or breastfeeding
• Have an allergy or hypersensitivity to any ingredient in Mounjaro
• Have a personal or family history of thyroid cancer
• Have multiple endocrine neoplasia type 2 (MEN-2)
• Have a history of pancreatitis (inflammation of the pancreas)
• Have severe digestive conditions such as Crohn's disease, ulcerative colitis, or gastroparesis (delayed stomach emptying)
• Have a history of gallstones (if you still have your gallbladder)
• Have diabetes-related eye problems (such as diabetic retinopathy)
• Have type 1 diabetes
• Have severe liver disease
• Have chronic kidney disease
• Have severe heart failure
• Have cancer requiring active treatment or monitoring every 6 months or more
• Have a current or past diagnosis of an eating disorder (except binge eating disorder)
• Have a history of solid organ transplant
• Have a history of epilepsy or porphyria

If any of these apply to you, your eligibility assessment will flag them before treatment starts. Be open about your full medical history so the right decisions can be made for you.

Medications we can't prescribe Mounjaro with

Some medications need very precise dosing to work safely, with regular blood tests to make sure the dose stays in a safe range. Voy is a remote service, so we can't offer this kind of monitoring. If you take any of the medications below, your weight loss treatment is best managed through your NHS GP.

The medications we can't prescribe Mounjaro alongside include:

Blood thinners: warfarin, acenocoumarol

Heart rhythm and heart medications: flecainide, propafenone, quinidine, procainamide, disopyramide, digoxin

Immunosuppressants: tacrolimus, ciclosporin, everolimus, sirolimus, azathioprine

Mood stabilisers: lithium

Epilepsy medications: phenytoin, carbamazepine (if prescribed for epilepsy), lamotrigine (if prescribed for epilepsy), oxcarbazepine, valproic acid, sodium valproate, primidone, phenobarbital, divalproex, ethosuximide, zonisamide

Antipsychotics: clozapine

Diabetes medications: insulin, sulfonylureas (such as gliclazide, glimepiride, glipizide, tolbutamide, chlorpropamide), other GLP-1 medications used for diabetes

Other weight loss medications: orlistat, Wegovy, retatrutide, Rybelsus

Other: methotrexate (if prescribed for cancer or IBD), theophylline, isoprenaline

If you take any of these, your prescriber will check during your eligibility assessment.

If you're on carbamazepine, lamotrigine, or methotrexate, you may still be eligible for Mounjaro through Voy. These are only excluded when used for specific conditions: carbamazepine and lamotrigine for epilepsy, and methotrexate for cancer or IBD. Your prescriber will check.

Medications you can take with Mounjaro

Metformin

You can take metformin alongside Mounjaro. The combination is generally well tolerated, and metformin doesn't cause low blood sugar on its own.

Metformin is most commonly prescribed for type 2 diabetes, but it's also used for PCOS. If you take it for type 2 diabetes, your blood sugar may improve once you start Mounjaro, so check in with your GP after a few months as your metformin dose may need adjusting.

Birth control and contraception

Mounjaro can reduce how well oral contraceptive pills are absorbed, which means they may not protect against pregnancy as reliably. This applies to combined pills (like Microgynon, Rigevidon, and Yasmin) and progestogen-only mini pills (like Cerazette, Cerelle, and desogestrel).

If you take any oral contraceptive, use a barrier method like condoms for 4 weeks after starting Mounjaro, and for 4 weeks after each dose increase.

You may also wish to consider switching to a non-oral method while you're on Mounjaro. Long-acting methods don't depend on absorption and aren't affected, including the Mirena coil, the copper coil, the implant, and the injection.

Blood pressure medication

Most blood pressure medications can be taken with Mounjaro. This includes:

• ACE inhibitors: ramipril, lisinopril
• Angiotensin receptor blockers: losartan, candesartan
• Beta blockers: bisoprolol, propranolol
• Calcium channel blockers: amlodipine, felodipine

As you lose weight on Mounjaro, your blood pressure tends to drop with it, which is one of the wider health benefits of weight loss treatment. If you're already on blood pressure medication, this can mean your medication eventually becomes too strong for what your body needs, and your GP may reduce your dose over time.

Tell your GP that you're starting Mounjaro so they can monitor your blood pressure more closely and adjust your medication when the time is right.

Levothyroxine

If you take levothyroxine for an underactive thyroid, you can continue it alongside Mounjaro, but your thyroid function will need monitoring.

Levothyroxine is sensitive to small changes in absorption, and Mounjaro's effect on the gut can alter how much you absorb. Your GP should check your thyroid function (a blood test for TSH) 8 weeks after you start Mounjaro, and 8 weeks after you reach a stable dose. Taking levothyroxine on an empty stomach, on a different day from your Mounjaro injection, may help keep levels stable.

This also applies to liothyronine if you take it instead of, or alongside, levothyroxine.

Antidepressants and anti-anxiety medications

You can take most antidepressants and anti-anxiety medications alongside Mounjaro.

SSRIs and similar antidepressants including sertraline, citalopram, escitalopram, and fluoxetine can be taken with Mounjaro. There's no documented interaction. Mounjaro slightly slows how quickly oral medications are absorbed, particularly when you first start treatment or move up a dose. This usually doesn't affect how well antidepressants work.

Mirtazapine and venlafaxine can be taken with Mounjaro. Mirtazapine in particular is known to increase appetite, so Mounjaro's appetite-suppressing effects may help offset weight gain that some people experience on it.

Propranolol, lorazepam, and diazepam can be taken with Mounjaro. None have a documented interaction.

A few things worth knowing if you're on any of these:

• Many antidepressants can cause nausea, diarrhoea, or tiredness, especially when you first start them or change your dose. Mounjaro can cause the same side effects, so if you're starting both around the same time, the overlap may feel more noticeable.
• Mounjaro can cause a small increase in heart rate (around 2 to 4 beats per minute). This is usually nothing to worry about, but if you have a history of anxiety, it might feel more noticeable at first.

If you notice changes in your mood or mental wellbeing after starting Mounjaro, reach out to the clinical team.

ADHD medications

ADHD medications can be taken with Mounjaro. There's no documented interaction. This includes:

• Methylphenidate (Ritalin, Concerta, Equasym, Medikinet, Xaggitin)
• Dexamfetamine (Amfexa)
• Lisdexamfetamine (Elvanse)
• Atomoxetine (Strattera)
• Guanfacine (Intuniv)

ADHD medications can suppress appetite on their own, and Mounjaro does the same. For some people, the combined effect can mean eating becomes harder than expected, particularly early on or after a dose increase.

Speak to your prescriber if:

• Your appetite drops to the point where you're struggling to eat
• You're losing weight faster than expected
• You feel weak, lightheaded, or unwell from not eating enough

Knowing your daily calorie needs can help you stay on track. Use our TDEE calculator to estimate your maintenance calories and a sustainable target.

HRT (hormone replacement therapy)

You can take HRT alongside Mounjaro. This includes oestrogen products like Oestrogel, Evorel, and Sandrena.

Most HRT applied to the skin (gels, patches, sprays) bypasses the gut entirely and isn't affected by Mounjaro. The Mirena coil also isn't affected.

Oral progesterone is different. Mounjaro slows how quickly your stomach empties, which can reduce how well oral medications are absorbed. For oral progesterone (like Utrogestan), this matters because it's what protects the lining of your womb. If you take oral progesterone, speak to your GP or HRT provider before starting Mounjaro. They may suggest switching to a non-oral form like the Mirena coil.

If you notice any unexpected bleeding while on both, speak to your provider.

For full guidance, see our article on Mounjaro and HRT.

TRT (testosterone replacement therapy)

You can take TRT alongside Mounjaro. This includes injectable testosterone (such as testosterone cypionate, enantate, or Nebido) and topical testosterone (such as Testogel, Testavan, or Tostran).

Injectable and topical testosterone aren't absorbed through the gut, so they're not affected by Mounjaro.

If your TRT plan also includes oral medications like tadalafil or sildenafil, these are fine to take with Mounjaro too. There are no documented interactions.

Hair loss treatments

You can take hair loss medications alongside Mounjaro. This includes finasteride, dutasteride, and minoxidil. These are available as oral tablets or topical treatments, and both are fine to take with Mounjaro.

Some people experience hair shedding during weight loss itself, which can happen with or without weight loss medication. This usually settles down as your weight stabilises.

Antibiotics

Most antibiotics can be taken with Mounjaro, including amoxicillin, flucloxacillin, and other penicillins.

Two things are worth knowing:

• Side effects can overlap. Both antibiotics and Mounjaro can cause nausea, vomiting, or diarrhoea. If you're already getting side effects from Mounjaro, you may want to consider skipping your weekly dose until you've finished your antibiotic course. Speak to your prescriber if you're not sure.
• Timing can matter. Some antibiotics need to be taken on an empty stomach or at specific times around meals, which can be trickier when Mounjaro slows digestion. Your pharmacist or GP can advise.

Painkillers

Paracetamol can be taken with Mounjaro. It's the safest first choice for pain relief and there's no interaction to worry about. Mounjaro may slightly delay how quickly paracetamol takes effect when you first start treatment, but this is short-lived and doesn't affect overall pain relief.

Ibuprofen and other NSAIDs (such as naproxen) are fine for occasional use. Regular or high-dose use is a different story. NSAIDs can irritate the stomach lining, and because Mounjaro also affects the gut, the combined effect can be uncomfortable. If you take any of these often or for ongoing pain, speak to your prescriber about whether paracetamol or another option would suit you better.

Co-codamol (paracetamol with codeine) can be taken with Mounjaro. Codeine can cause constipation, which is also a possible side effect of Mounjaro, so the two together can sometimes worsen this. Drinking plenty of water and staying active can help.

Antihistamines

Antihistamines can be taken with Mounjaro. There are no known interactions. This includes:

• Cetirizine (Piriteze, Zirtek, Benadryl)
• Loratadine (Clarityn)
• Fexofenadine (Telfast, Allevia)
• Chlorphenamine (Piriton)
• Promethazine (Phenergan, Sominex)
• Diphenhydramine (Nytol Original, used as a sleep aid)

Sedating antihistamines (like chlorphenamine, promethazine, and Nytol) can cause drowsiness. This is worth knowing if you're already feeling tired from changes in food intake on Mounjaro.

Herbal supplements, vitamins, and other supplements

Tell your prescriber about any supplements you take at your consultation.

Herbal supplements

Most herbal supplements are fine to take with Mounjaro. Ashwagandha, lion's mane, and echinacea can all be taken without specific concerns.

A few need a closer look:

• St John's Wort can speed up how the liver breaks down many medications. The direct interaction with Mounjaro hasn't been studied, but if you take St John's Wort, it's worth being aware that it may affect how Mounjaro works. Mention it at your consultation so your treatment can be monitored.
• Ginseng and fenugreek can both lower blood sugar in some people. On their own, this usually isn't a concern. But if you're also on diabetes medication that lowers blood sugar (like metformin), the combined effect could push your blood sugar too low. Watch out for shakiness, sweating, dizziness, or feeling unusually hungry, and speak to the clinical team if these happen.

Vitamins and other supplements

Standard vitamins and supplements are generally fine alongside Mounjaro, with no known interactions. This includes:

• Multivitamins
• Vitamin D
• Collagen
• Protein powder
• Creatine
• Fibre supplements

Alcohol and Mounjaro

You can drink alcohol on Mounjaro, but it's best to limit it.

Alcoholic drinks are high in calories and can stimulate appetite for some people, both of which work against your weight loss goals. Mounjaro and alcohol can both cause nausea, stomach upset, and dehydration, so the combined effect can be worse than either on its own.

One thing worth knowing: as you lose weight, your alcohol tolerance can drop. The same amount of alcohol that didn't affect you before may hit harder once you're lighter.

Recreational drugs and Mounjaro

If you use recreational drugs, it's worth being upfront when you fill in your eligibility questionnaire. The clinician reviewing your answers can then make the best decision for your treatment. This isn't about judgement, it's about making sure your treatment plan is safe.

Many recreational drugs affect things Mounjaro also affects, like appetite, digestion, blood sugar, and heart rate. Combined with Mounjaro, the effects can be more pronounced than expected.

What to tell your prescriber before starting

There's a lot to think about, but you don't need to figure it all out alone. Your eligibility questionnaire asks about your medications, medical history, and lifestyle, and a clinician will review your answers before deciding whether Mounjaro is right for you.

To make the most of your consultation, be ready to share:

• All prescription medications you take, including the dose
• Any over-the-counter medications you use regularly
• All supplements, vitamins, and herbal products
• Your full medical history, including any of the conditions listed in Who shouldn't take Mounjaro? above
• Whether you're trying to conceive, pregnant, or breastfeeding

Being upfront means the clinician reviewing your answers can give you the safest possible care.