Medicines and food

The following are some examples of how some foods can interact with some medicines.

Grapefruit

Eating grapefruit or drinking grapefruit juice can affect some medicines. In most cases, it increases the level of the medicine in your blood. This can increase the risk of side effects or change the effect the medicine has. Learn more about grapefruit and medicines. 

Dairy products such as milk, cheese and yoghurt

The calcium in these products may bind to some medicines such as iron supplements or some antibiotics. This means that less medicine is absorbed into the body. To avoid this problem, it’s best to allow enough time between having dairy products and taking your medicines. Don’t take them together. Read the label of your medicine to check for any warnings or instructions about dairy. 

Foods rich in tyramine

Some foods are high in tyramine, such as mature cheese, pickled herring, broad bean pods, meat extracts (eg, Bovril) and yeast extract (eg, Marmite and Vegemite), soy sauce and miso. Medicines called monoamine oxidase inhibitors (MAOIs) block monoamine oxidase, which is an enzyme that breaks down excess tyramine in the body. If you are taking these medicines and have foods high in tyramine, this can cause your blood pressure to rise suddenly, which can be very dangerous. A warning sign may be a throbbing headache. Read more about MAOIs and a low tyramine diet(external link). 

• If you are taking tranylcypromine, you should completely avoid tyramine-rich food.
• If you are taking moclobemide or linezolid, you should avoid consuming large amounts of tyramine-rich food.

Sudden changes in diet

People taking some medicines such as warfarin need to take care with what they eat and drink. Warfarin is affected by vitamin K-rich food such as broccoli, brussels sprouts, green leafy vegetables and liver. While it’s not necessary to avoid these foods completely, sudden changes in diet that significantly increase or decrease vitamin K-rich foods which can affect the way warfarin works. Read more about warfarin and diet. 

Other medicines such as empagliflozin (Jardiamet) or Jardiance, can also be affected by significant changes to your diet, such as if you suddenly start eating less or go on a keto (low carbohydrate) diet. This could increase your risk of side effects (ketoacidosis).

Some medicines need to be taken 'before food' or 'on an empty stomach'. If the instructions say that you should take your medicine on an empty stomach, take it at least an hour before or 2 hours after a meal. This means you can 
take your medicine first and eat one hour later, OR you can eat first and take the medicine 2 hours later.

Why should some medicines be taken on an empty stomach?

Taking some medicines at the same time as eating may prevent your body absorbing the medicine, and it may not work as well as it should. This is because food, and even some drinks, can affect the way these medicines work.

Here are examples of some medicines that are best taken on an empty stomach, although there may be others that are not on this list:

• thyroxine (also called levothyroxine or Eltroxin®)
• Fosamax (also called alendronate)
• flucloxacillin.

Forgetting these instructions on rare occasions is unlikely to do any harm, but taking these medicines with food regularly may mean they won't work so well.

If the instructions say to take your medicine with or just after food, a small amount of food is usually enough.

Why should some medicines be taken with food?

Here are common reasons why some medicines should be taken with food.

• To reduce side effects of nausea or vomiting. With medicines that can cause nausea or vomiting, taking the medicine after a meal can reduce these side effects. Examples include allopurinol and metronidazole.
• To reduce side effects of stomach upset, including indigestion, stomach inflammation or ulcers. Some medicines can irritate your stomach, and taking them with food reduces this effect. Something like biscuits, a sandwich or a glass of milk is usually enough. Medicines that can cause an upset stomach include: 
  • aspirin
  • non-steroidal anti-inflammatory drugs (NSAIDs), such as diclofenac and ibuprofen
  • steroid medication (corticosteroids), such as prednisolone and dexamethasone.
• To treat problems such as heartburn, reflux or indigestion. Medicines called antacids are taken to prevent heartburn, reflux and indigestion, which usually occur when acid is produced as food enters your stomach. Therefore, these medicines are most effective if taken immediately after, or during, a meal.
• To ensure the medicine is absorbed into your bloodstream properly. You need food in your stomach and gut for your body to absorb some medicines properly.
• To help your body process the meal. Some medicines for diabetes, if taken by mouth, should usually be taken around mealtimes to reduce blood sugar levels after eating and to avoid very low blood sugar (hypoglycaemia). Enzyme supplements, which can be used to help people with chronic pancreatitis, should also be taken with food to help your body process the meal.