When you pick up your prescription at the pharmacy or buy over-the-counter medicine, you might notice the instructions on the label say “Take with food” or “Take on an empty stomach.” This is because when you take oral medications, they travel to your gut and are mostly absorbed in the small intestine, from where it goes to the liver and then into your bloodstream to be transported to the intended destination. Food can affect this process. For this reason, some medicines should be taken with or without food to be effective. Besides affecting how well a medication works, food can also affect the drug side effects. So, to get the most out of your treatment, it’s important to follow instructions from your health professional and the drug label. 

Please continue reading to learn more about why you should take certain medications with meals.

Why do you need to take certain medications with food?

To reduce nausea and vomiting

Some medications can cause nausea and vomiting as side effects. Taking these medications with food can help to ease symptoms of feeling sick. Examples include certain antidepressants,  antibiotics, and other medications such as bromocriptine, and allopurinol. 

To reduce stomach irritation

Certain medicines can irritate the stomach, causing stomach upset, stomach inflammation, and stomach problems like ulcers. Taking these medications with foods or even snacks can help to reduce these side effects. Examples include nonsteroidal anti-inflammatory drugs (aspirin, ibuprofen, diclofenac) and steroids (prednisone, dexamethasone).

To help the body process a meal

Diabetes medicines such as glimepiride and gliclazide are taken to reduce blood sugar levels after eating. They should be taken with food to help process a meal and reduce the risk of hypoglycemia (low blood sugar). Enzyme supplements, given to people with chronic pancreatitis, are also taken at mealtimes to help the body process the food.

To treat heartburn or acid reflux

When food enters the stomach, acid is produced to digest it. Antacids are medicines that are taken to prevent indigestion, acid reflux, and heartburn symptoms that occur due to stomach acid. Depending on the type of medications, there may be different instructions for administration. For example, antacids work best if taken during or immediately after a meal when stomach acid production is high. While pantoprazole (Protonix) can be taken anytime, it is best to take this medication in the morning, before or during breakfast. 

To prevent the medicine from being washed away

Some medicines are in the form of mouthwash and are used to treat oral thrush or mouth ulcers. These medicines must be used after meals because eating food washes away the medicine before it has had time to work. Examples include miconazole gel and liquid nystatin.

To ensure proper absorption

Food triggers many changes in the gut, such as increased blood flow, changes in motility, and changes in pH (acidity). These changes can affect how much medicine is absorbed from the gut into the bloodstream, which can impact how well the medicine works. Some medicines are absorbed better when there is food in the stomach. Examples include ritonavir, a medicine used to treat HIV, and itraconazole capsules and tablets used to treat fungal infections. 

Why should some medications be taken on an empty stomach?

You should take some medications on an empty stomach or away from meals because the presence of food in the gut leads to physiological changes and affects how the medications work. 

For instance, food can reduce the absorption of some medications, making the medication less effective. Examples include thyroid replacement medications such as levothyroxine (Synthroid) and medicines used to treat osteoporosis, such as alendronate (Fosamax) and ibandronate (Boniva). Also, eating foods high in calcium, such as dairy products, can prevent the body from absorbing some antibiotics.

Other medications are sensitive to gut secretions. An acidic environment can make certain antibiotics such as phenoxymethylpenicillin (penicillin V) less effective, and therefore these medicines are best taken on an empty stomach.

Specific foods can cause problems by allowing more of the drug to enter the bloodstream and putting you at risk of having dangerously high levels of the medicine. An example is grapefruit juice, which can lead to increased absorption of medications such as certain statins used to lower cholesterol (Zocor, Lipitor), some medications used to treat high blood pressure (Procardia, Adalat CC) and abnormal heart rhythm (Pacerone, Cordarone), and some anti-anxiety drugs (BuSpar).

In general, medications that are best taken on an empty stomach should be taken at least half an hour before eating or two hours after you’ve eaten food. 

References:

1. https://www.nhs.uk/common-health-questions/medicines/why-must-some-medicines-be-taken-with-or-after-food/
2. https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mix