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Can intermittent fasting interact with medication?

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IbuprofenAntibioticsImmunosuppressantsAntipsychoticsAcne medicationsSpeaking with a doctorSummary
Intermittent fasting can be a good way to help you manage weight and have better health in general. But it can also affect how well certain medications work.
Medically reviewed by Alyssa Walton, PharmD
Written by D. M. Pollock
Updated on

Intermittent fasting involves limiting your eating to scheduled meal times. This way of eating may help you manage weight and improve heart health and inflammation.

But everyone is different, and intermittent fasting may not work for you as it may for someone else. It’s important to know that intermittent fasting can affect the function and effectiveness of certain medications.

If you want to try intermittent fasting and are taking any medications for existing conditions, it’s important to speak with a doctor first. They can advise on whether it’s safe for you to do so.

Medications that may interact with intermittent fasting include:


Ibuprofen (Advil) is a pain relief medication that’s available over the counter (OTC). It’s a nonsteroidal anti-inflammatory drug (NSAID). The drug works by blocking the activity of enzymes that trigger inflammation at the point of pain.

Ibuprofen can help manage pain or discomfort due to:

Ibuprofen can have side effects on your digestive system and kidneys. This is because ibuprofen lowers the amount of prostaglandins in your body, which are responsible for creating the protective lining around your stomach.

This is why healthcare professionals typically advise you to eat before you take ibuprofen. But if you’re practicing intermittent fasting and taking ibuprofen on an empty stomach, this can lead to serious complications.

Serious complications can include:

Taking ibuprofen regularly on an empty stomach can be dangerous. If you need OTC pain relief medication and wish to intermittently fast, consider speaking with a doctor about an alternative option.

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Antibiotics are important medications that can help the body fight off bacterial infections. Certain antibiotics require you to eat beforehand for the medication to work effectively. Eating beforehand can also help prevent serious side effects, such as:

  • nausea
  • vomiting
  • diarrhea

Antibiotics that require taking alongside food include:

If a doctor prescribes antibiotic medication for you, it’s important to follow the doctor’s instructions. You can also refer to the instructions on the label of your medication. If you’re not sure whether you need to take food before or after taking antibiotics, consider speaking with a doctor or pharmacist.


Immunosuppressants are medications that help lower the activity of your immune system. A healthcare professional might likely prescribe immunosuppressants if you undergo transplant surgery. This is to help prevent your body from rejecting the transplanted organ.

A common type of immunosuppressant medication is calcineurin inhibitors (CNIs). But according to a 2021 review, fasting can lower the effectiveness of CNI medications.

So if you’re taking immunosuppressants and fasting for 12 hours or more for religious purposes, such as during Ramadan, consider speaking with a healthcare professional. They can suggest alternative medication options when possible.


Antipsychotic medications, such as olanzapine (Zyprexa), can help ease symptoms of psychosis. They work by blocking the activity of dopamine, a neurotransmitter that, in excess, can cause psychosis.

A common side effect of antipsychotics, like olanzapine, is weight gain. This happens because they may change your dopamine levels, which can then affect how your metabolism works and lead to weight gain.

An animal study from 2022 notes how intermittent fasting can lower the changes to metabolism from olanzapine in male mice.

While more research is needed to show how this may be effective for humans, it’s possible that intermittent fasting may help if you experience weight gain from taking olanzapine.

Acne medications

Oral isotretinoin (Absorica) is a retinoid medication that healthcare professionals may prescribe if you’re experiencing acne. It’s important to take this medication with a meal, as the medication comes in a lipid-soluble capsule. This means that it works best if you consume a high fat meal with the tablet.

You can take these medications while fasting. But you may not experience the full effects of the medication, as doing so will alter how your body absorbs the drug.

When should you speak with a doctor?

Two people sat on a couch eating from bowls.
Photography by Westend61/Getty Images

If you’d like to try intermittent fasting but are taking medication regularly, it’s a good idea to speak with a doctor first. This is because both OTC and prescription medications can interact with a lack of food in your stomach, making them less effective.

A doctor can help you create a fasting plan that fits with when you need to take your medication. This would make your medication work better and let you try a new and beneficial diet without missing out.

In some cases, a doctor can prescribe an alternative medication that’s suitable for fasting.


Intermittent fasting can have a positive effect on some people. It may help you manage weight, among other benefits. But if you’re taking medication regularly, it’s important to speak with a doctor before trying a fasting regime.

Taking certain medications on an empty stomach may not cause side effects or affect how well they work. But for other medications, avoiding food can lower their absorption or worsen side effects. A doctor can adjust your treatment plan to accommodate fasting.

Download the free Optum Perks Discount Card to save up to 80% on some prescription medications.

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