The effectiveness of many medications depends not just on the dose prescribed, but also on when and how they are taken in relation to food. Certain foods can interfere with drug absorption, alter how medications are broken down in the body, or increase the risk of side effects. In some cases, taking a drug with the wrong food can reduce its effectiveness by 50–90%.
Most of the time food-related instructions are often overlooked but understanding these drug interactions can make a meaningful difference to treatment outcomes.
Dr. Sermed Mezher, a family physician, highlighted this gap in an Instagram video, he said ,“Food instructions are commonly missed when prescribing meds, I’ve done it myself. but they can make a pretty significant difference.”
Food–drug interactions occur when foods or beverages alter the absorption, metabolism, or action of a medication, potentially reducing effectiveness or increasing the risk of side effects.
A drug interaction occurs when a substance affects how a medication works in the body. The effect may increase or decrease the drug’s action, or lead to unwanted side effects.
Physicians and pharmacists are well aware that some foods and medications, when taken together, can prevent the body from properly utilizing the drug or in some cases can cause harm, this is termed as Food-Drug interaction.1
Doxycycline is a widely used broad-spectrum tetracycline antibiotic.
Tetracycline antibiotics bind to multivalent cations such as calcium, iron, magnesium, and aluminum. This process is known as chelation forms an insoluble compound in the gut, preventing the drug from being absorbed and leading to its excretion in urine or feces. 3
Milk and other dairy products
Antacids containing aluminum or magnesium
Iron and zinc supplements
When taken together, these can markedly reduce absorption, sometimes by more than half, particularly with repeated dosing.
Dr. Mezher noted: “Quinolones such as ciprofloxacin or levofloxacin shouldn’t be taken with milk.”
According to NHS guidance on ciprofloxacin:
Do not take tablets or liquid with dairy products (milk, cheese, yogurt)
Avoid drinks with added calcium, including some fortified dairy-free milks
Leave a gap of at least 2 hours between ciprofloxacin and having above mentioned type of food and drink
While regular meals have minimal impact on quinolone absorption, metallic cations significantly interfere by forming insoluble complexes with the drug. This reduces how much medication enters the bloodstream.
General recommendations suggest taking quinolones 1–2 hours before, or 3–4 hours after, any product containing calcium, iron, magnesium, or aluminum. 4
Even medications within the same class can have different food-related instructions.
Dr. Mezher explained: “Even within the same drug class, there can be variations, amoxicillin should ideally be taken with food, but others like Penicillin V should be taken on an empty stomach.”
Amoxicillin
Can be taken before or after food
Phenoxymethylpenicillin (Penicillin V)
It's best not to take phenoxymethylpenicillin at mealtimes
Take 30 minutes before a meal or at least 2 hours after eating
Food can significantly reduce its absorption
Not all clinically significant food–drug interactions involve antibiotics. Other well documented examples include: 1
Grapefruit juice, which can inhibit intestinal enzymes and increase blood levels of certain statins, calcium channel blockers, and immunosuppressants
Vitamin K rich foods such as spinach and kale, which can reduce the effectiveness of warfarin by opposing its anticoagulant action
Foods containing tyramine, including aged cheeses and cured meats, which can cause dangerous blood pressure elevations when combined with monoamine oxidase inhibitors
It's important to know which medications should be taken with food and which should be taken on an empty stomach, because food can significantly change how a drug is absorbed, broken down, or tolerated by the body.
Some medications work better with food because meals help increase their absorption or reduce stomach irritation.
Example include: Amoxicillin
Food can block absorption and reduce effectiveness for:
Phenoxymethylpenicillin
Tetracycline antibiotics
Certain thyroid medications
Some osteoporosis treatments
Incorrect timing can mean you are not receiving the full therapeutic benefit of your medication even if you never miss a dose.
"It’s important to know which medications should be taken with food and which should be taken on an empty stomach, because food can significantly change how a drug is absorbed, broken down, or tolerated by the body," said Dr. Mezher.
“Certain antibiotics, thyroid medications, and osteoporosis treatments can become far less effective if taken with food, while others like anti-inflammatories can damage the stomach if taken without it,” he further explained.
Can I take antibiotics with milk?
Some antibiotics such as tetracyclines and quinolones should not be taken with milk or dairy products because calcium can reduce their absorption.
Why do some medicines need to be taken on an empty stomach?
Food can delay or block absorption of certain medications, preventing them from reaching effective levels in the bloodstream.
Are food–drug interactions common?
Yes. Many commonly prescribed medications are affected by food, which is why timing instructions are an important part of safe medication use.
Bushra, R., Aslam, N., and Khan, A. Y. “Food Drug Interactions.” Oman Medical Journal 26, no. 2 (2011): 77–83. https://doi.org/10.5001/omj.2011.21.
Neuvonen, P. J. “Interactions with the Absorption of Tetracyclines.” Drugs 11, no. 1 (1976): 45–54. https://doi.org/10.2165/00003495-197611010-00004.
Shutter, M. C., and Akhondi, H. “Tetracycline.” In StatPearls. Treasure Island, FL: StatPearls Publishing, 2025. https://www.ncbi.nlm.nih.gov/books/NBK549905/.
Yan, A., and Bryant, E. E. “Quinolones.” In StatPearls. Treasure Island, FL: StatPearls Publishing, 2025. https://www.ncbi.nlm.nih.gov/books/NBK557777/.
Disclaimer: This information is for educational purposes only and does not replace professional medical advice.