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Nutrition and daily life

Food and medicines: with what, and when

Some foods change how medicines are absorbed or broken down. In leukemia treatment this matters especially: tyrosine kinase inhibitors, antifungals and immunosuppressants are sensitive to food. This section covers the main rules.

Last updated: ~1 min read
Grapefruit and pomelo in shadow.
Figure 1.Grapefruit aside — Food and medicines: with what, and when

01Short answer

Ask your pharmacist whether each medicine is taken on an empty stomach or with food, and stick to it. Grapefruit, pomelo, Seville oranges and their juices raise blood levels of many medicines (for example some TKIs, ciclosporin and tacrolimus), so avoid them. Milk, calcium, iron and antacids reduce absorption of some medicines; a time gap may be needed. If you take warfarin, do not suddenly change how many vitamin K-rich green vegetables you eat. Take medicines with water.

02Simple explanation

Empty stomach or with food: ask.

No grapefruit.

Milk and calcium: leave a gap.

Medicines with water.

03Scientific explanation

FDA: grapefruit juice blocks the CYP3A4 enzyme in the gut and can dangerously raise blood levels of some medicines.

NCCIH: "natural" does not mean "safe"; the contents and quality of supplements are not checked as strictly as medicines.

04What happens in the body?

Posaconazole and others

Some medicines are absorbed better with a fatty meal; check the leaflet.

Medicines and food
Figure 2.Medicines and food — Food and medicines: with what, and when

Alcohol

It interacts with many medicines and strains the liver.

A pharmacy counter with a blank leaflet.
Figure 3.The pharmacist — Food and medicines: with what, and when

Interactions

Supplements can change medicine levels in the blood through liver enzymes such as CYP3A4.

Food first

A varied diet usually provides the vitamins you need; supplements only when there is a need.

05Supplements: four steps

List them, show your team, check the evidence, take only with agreement.

List — Write everything down.1ListWrite everything down.
Show — Doctor and pharmacist.2ShowDoctor and pharmacist.
Check — Evidence and risk.3CheckEvidence and risk.
Agree — Only with approval.4AgreeOnly with approval.
OpennessTell everything.
FoodPlate first.
SafetyInteractions.

06Key points at a glance

TopicIn brief
Posaconazole and othersSome medicines are absorbed better with a fatty meal; check the leaflet.
AlcoholIt interacts with many medicines and strains the liver.
InteractionsSupplements can change medicine levels in the blood through liver enzymes such as CYP3A4.
Food firstA varied diet usually provides the vitamins you need; supplements only when there is a need.

07Key terms

CYP3A4
An enzyme that breaks down many medicines.
TKI
A tyrosine kinase inhibitor, such as imatinib.
Dietary supplement
A product of vitamins, minerals, herbs or other substances.
Interaction
One substance changing the effect of another.

08Key points

  • Ask the rule.
  • Avoid grapefruit.
  • Watch the timing.
  • A supplement is not a treatment.
  • Report every one.

09Frequently asked questions

Are oranges OK?

Ordinary sweet oranges usually are; Seville (bitter) oranges are not.

Can I take my medicine with juice?

Water is best unless told otherwise.

Is a "natural" supplement harmless?

No. Natural substances can also act strongly and interact.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Are oranges OK?

  2. Can I take my medicine with juice?

  3. Is a "natural" supplement harmless?

My questions

12Sources

  1. U.S. Food and Drug Administration. Grapefruit Juice and Some Drugs Don't Mix
  2. NIH Office of Dietary Supplements. Dietary Supplement Fact Sheets
  3. NCCIH. Using Dietary Supplements Wisely
  4. National Cancer Institute. Complementary and Alternative Medicine
  5. Memorial Sloan Kettering. About Herbs, Botanicals and Other Products
  6. European Food Safety Authority (EFSA). Salmonella
  7. Harvard T.H. Chan School of Public Health — The Nutrition Source. Protein
  8. U.S. FDA. Advice about Eating Fish
  9. MedlinePlus. Prednisone
  10. World Health Organization. Brucellosis fact sheet
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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