What can food-drug interactions cause?

The interaction between foods and medications can cause:

  • Medications to work faster or slower, better or worse;
  • Cause a side effect from a medicine to get worse or better;
  • Cause a new side effect, or;
  • Reduce or enhance the absorption of certain nutrients in food.

What foods can cause food-drug interactions?

Any type of food is capable of causing food-drug interactions, depending on the following factors:

  • Type and dosage of medication(s);
  • Timing of intake of food - for example, on an empty or full stomach;
  • An individual's age, weight and gender;
  • Existing medical conditions, and;
  • Use of vitamins, herbal or dietary supplements.

Importantly, caffeine and alcohol can also cause food-drug interactions.

Does it matter if I take medicine on a full or empty stomach?

For certain medicines, taking food on a full or empty stomach can have a significant effect on its function. This is because the digestive process that breaks down the food we eat, can also affect medicines. Unfortunately, there is no general rule on when is the best time to take medicines. This differs greatly between medicines. Therefore, it is important to follow the directions on the medicine label, or ask your doctor or pharmacist for advice.

Below are explanation of common instructions found on medicine labels.

Instruction: Take on an empty stomach.
Explanation Examples
Take 1 hour before meals or 2 hours after meals. Some antibiotics don't work as well if taken with food.
Instruction: Don't take with certain foods.
Explanation Examples
Don't take within 1 hour before or 2 hours after meals containing the specified food to avoid. Some osteoporosis medications don't work well when taken with calcium-rich foods, such as milk, yoghurt and calcium supplements.
Instruction: Don't eat certain foods at all.
Explanation Examples
Avoid taking the specified food altogether while on the medication. Some cholesterol-lowering medicines, heart medicines and several other common medicines are affected by grapefruit juice. Even a small amount of grapefruit juice can have a significant effect on these medicines.
Instruction: Eat consistent amounts of certain foods.
Explanation Examples
Don't change your diet during the course you are on the medication. Warfarin (known as Coumadin or Marevan), a blood-thinning medicine, is affected by vitamin K in the diet. Rather than avoid vitamin K-rich foods altogether (such as green vegetables, egg yolks, chickpeas or lentils), it is preferable to eat a consistent amount of these foods. This will allow your doctor to prescribe a predictable dose of warfarin, which prevents unwanted complications.
Instruction: Take with meals.
Explanation Examples
Take at meal times or up to half an hour before or after meals. Non-steroidal anti-inflammatory drugs (NSAIDs) that are commonly used as pain-relief medications (such as ibuprofen or aspirin), can cause indigestion and stomach ulcers if taken on an empty stomach.
Instruction: Take at the same time, each time.
Explanation Examples

Take at the time directed by your doctor or pharmacist.

Generally, even if not advised, taking medicines at a set time each day also helps you remember to take them.

Frusemide, a heart medication, is taken at set times of the day (morning and/or lunchtime) to reduce unnecessary side effects, such as frequent urination at night.


Chemical substances that kill or suppress the growth of bacteria.


A type of fat produced by the body that is necessary for metabolism.


Non-steroidal anti-inflammatory drugs are commonly used to manage arthritis-related pain and inflammation and other musculoskeletal disorders. NSAIDs include aspirin and ibuprofen.

Does it matter if I take medicine with alcohol?

In general, alcohol tends to affect most medicines. This is because both alcohol and most medicines are broken down by the liver. Therefore, alcohol competes with these medicines leading to:

  • The medicines working faster or slower;
  • Increased or new side effects, or;
  • Alcohol lasting in your system longer.

In most cases it is best to not take medicines with alcohol. Take medicines either one hour before drinking alcohol or once alcohol is no longer in your system.

Does caffeine affect the medicines I take?

Caffeine, which is the active ingredient in coffee, but also found in tea, many soft drinks and even chocolate, can interact with certain medicines. In fact, caffeine is deliberately added to some prescription and over-the-counter medicines to treat tiredness and improve the effect of some pain-relief medicines. However, studies have shown that drugs like antidepressants, thyroid medicines and osteoporosis drugs can be affected by coffee. The absorption of osteoporosis and thyroid medicines can be reduced by coffee, whereas some antidepressants, antibiotics and certain asthma drugs can increase caffeine's effects, causing a rapid heart rate and a jittery feeling. Usually, moderate intake of coffee is generally safe (less than four cups per day). However, it is best to discuss this with your doctor or pharmacist if you are concerned.


Chemical substances that kill or suppress the growth of bacteria.


Medication used to treat depression and other mood disorders.

Common food-drug interactions

The following is a list of conditions for which food and drug interactions are common. It is not complete and is intended as a guide only. Always read the label and speak to your doctor and pharmacist before trying any new medications or changing your dosage.

Condition Medicine
Allergies Antihistamines are a class of medications commonly used to treat allergies. There is a range of antihistamines, some of whom cause drowsiness.
Examples Interactions




Alcohol can interact with antihistamines, making you even drowsier.

Condition Medicine
Heart conditions ACE (angiotensin converting enzyme) inhibitors are used to lower blood pressure and treat heart failure.
Examples Interactions




ACE inhibitors increase the level of potassium in your body. Too much potassium can cause heart palpitations and abnormal heart rhythms, so if you take ACE inhibitors, it is best to limit the amount of foods that are high in potassium, such as bananas, dried apricots and green leafy vegetables. Only use potassium supplements if advised by your doctor.

Condition Medicine
Heart conditions Beta-blockers are a class of medications used to reduce the strain on the heart by slowing the heart rate, reducing the strength of the heartbeat, and lowering blood pressure.
Examples Interactions



Carvedilol is best taken with food. Carvedilol tablets are not meant to be crushed, chewed or split. Extended-release capsules are best taken in the morning with food. Metoprolol is best taken with a meal or immediately after a meal.

Condition Medicine
Heart conditions Diuretics work to remove water, sodium and chloride from your body. They can be used to treat high blood pressure (hypertension).
Examples Interactions




Diuretics can be taken with food if they cause an upset stomach.

Some diuretics can result in decreased levels of potassium, magnesium and calcium, while others have the opposite effect - they raise the level of potassium by blocking the kidneys' excretion of it.

To avoid the complications associated with abnormal potassium levels, it is important that you talk to your doctor or pharmacist for specific advice about the medicine you are taking.

Condition Medicine
Heart conditions Statins lower the production of 'bad' cholesterol (low-density lipoprotein - LDL). Some of them also lower triglycerides, or increase 'good' cholesterol (high-density lipoprotein - HDL).
Examples Interactions





Most statins can be taken on a full or empty stomach.

Grapefruit juice is best avoided as it can increase the chances of side effects.

Alcohol is also best avoided while taking statins as it can result in liver damage.

Condition Medicine
Heart conditions Digoxin is a medication that makes the heart beat more slowly and with more force.
Examples Interactions

Digoxin is best taken an hour before or two hours after eating.

High-fibre foods can lower the amount of digoxin in your body, so digoxin is best taken at least two hours before eating foods high in fibre.

Senna and St John's wort can also lower the level of digoxin and are best avoided.

Black liquorice taken with digoxin can cause irregular heartbeats and heart attack, so it too is best avoided.

Digoxin is meant to be taken at the same time every day. Follow the directions on the label and from your doctor carefully.

Condition Medicine
Heart conditions Nitrates reduce blood pressure by dilating blood vessels in the body.
Examples Interactions

Isosorbide dinitrate


Alcohol is best avoided, as it can further relax the blood vessels, which can lead to dangerously low blood pressure.

Condition Medicine
Heart conditions Anticoagulants are a class of medications used to reduce blood clotting. They are used to prevent disorders caused by blood clots.
Examples Interactions



Warfarin can be taken on a full or empty stomach.

Eating large amounts of foods that are high in vitamin K, or suddenly changing the amount of them you eat, can make warfarin treatment less safe and effective. Examples of foods high in vitamin K include broccoli, spinach, brussel sprouts, cabbage and turnip.

Condition Medicine
Chronic pain and arthritis Pain-relieving medications (analgesics).
Examples Interactions



Non-steroidal anti-inflammatory drugs (NSAIDs)

Alcohol can interact with pain-relieving medications, increasing the chances of liver damage, causing drowsiness (with codeine and morphine), and resulting in stomach bleeding (with NSAIDs).

It is a good idea to take food with NSAIDs to prevent any stomach upsets.

Condition Medicine
Heartburn Proton pump inhibitors decrease the amount of stomach acid.
Examples Interactions




Esomeprazole and omeprazole are best taken at least an hour before a meal.

Pantoprazole can be taken on a full or empty stomach.

Condition Medicine
Hypothyroidism Thyroid hormone replacement.
Examples Interactions
Thyroxine Levothyroxine is best taken on an empty stomach in the morning, at least 30-60 minutes before eating.

Condition Medicine
Infections Depending on the type of infection, a range of different medications can be used.
Examples Interactions




Alcohol is best avoided.

Condition Medicine
Osteoporosis Biphosphonates are used in the prevention and treatment of osteoporosis. They work by preventing the breakdown of bone and improving bone density.
Examples Interactions




Biphosphonates only work when taken on an empty stomach. They are best taken early in the morning with a small amount of plain water, not mineral water.

Do not lie down for least 30 minutes after taking alendronate or risedronate, or for an hour after taking ibanodronate.

Condition Medicine
Mental health Benzodiazepines are a family of medications used to treat anxiety disorders and panic attacks.
Examples Interactions





Alcohol is best avoided as it can worsen the medications' side effects, such as drowsiness.

Condition Medicine
Mental health Antidepressants are used to treat a range of problems, not just depression.
Examples Interactions






Antidepressants can be taken on a full or empty stomach.

Paroxetine is meant to be swallowed whole, and not to be crushed or chewed.

Alcohol is best avoided as it can worsen the medications' side effects, such as drowsiness.

Condition Medicine
Mental health Antipsychotics are used to treat bipolar disorder and schizophrenia.
Examples Interactions





Ziprasidone capsules are meant to be taken with food.

The other medications can be taken on a full or empty stomach.

When taking clozapine, it is best to avoid caffeine, as it can increase the levels of the drug in your blood, resulting in side effects.

Alcohol taken with any antipsychotic medication can worsen its side effects, such as drowsiness.

Condition Medicine
Mental health Mood stabilisers are medications given to treat the symptoms of bipolar disorder. It is not yet completely clear how they work.
Examples Interactions




Lithium is meant to be taken immediately after a meal.

Lithium can result in sodium loss, so it is necessary to maintain a diet that includes salt and plenty of water.

Alcohol is best avoided because it can worsen the medications' side effects, such as drowsiness.

Condition Medicine
Sleep disorders Sedatives and hypnotics are medications given to people who have difficulty sleeping.
Examples Interactions



It is best not to take these medications with or immediately after a meal, or while drinking alcohol.

ACE inhibitors

Angiotensin-converting enzyme (ACE) inhibitors are medications that allow the blood vessels to relax and dilate. They can be used to treat high blood pressure and heart failure.


Chemical substances that kill or suppress the growth of bacteria.


Medication used to treat depression and other mood disorders.


A substance that counters the physiological effects of histamine, a type of compound released by the tissues as an inflammatory response to an allergic reaction.


Substances that hinder the activity of hormones such as adrenaline by blocking the beta receptors, found in many organs but particularly the heart and blood vessels. These are used to treat a range of conditions including high blood pressure and migraines.


A type of fat produced by the body that is necessary for metabolism.


A substance that promotes the production and excretion of urine.


Entry into the body of microorganisms that can reproduce and cause disease.


A metal element that is used in medications that treat psychiatric illnesses.


Non-steroidal anti-inflammatory drugs are commonly used to manage arthritis-related pain and inflammation and other musculoskeletal disorders. NSAIDs include aspirin and ibuprofen.

Panic attacks

An acute episode of extreme and overwhelming anxiety.

Proton pump inhibitors

Medications that inhibit or reduce the activity of proton pumps (proteins that move protons, or hydrogen atoms, across cell membranes in the body). These medications can be used to reduce the production of gastric acid in order to treat peptic ulcers and heartburn.


A chemical element and important micronutrient in the diet. It is present in salt and plays an important role in how the body controls blood pressure.


A type of medication that lowers cholesterol and can be used to prevent cardiovascular disease.


A water-soluble compound and major mineral that is essential for maintaining contractions of muscles, including the heart.


The process by which blood changes from a liquid to a semi-solid state, usually to seal off any sites of bleeding. This is also known as coagulation.

Bone density

Also known as bone mineral density, it is a measure of bone strength calculated as the mineral content per square centimetre of bone. The higher the mineral content, the denser and stronger the bones.

FAQ Frequently asked questions