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 times 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.”
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 reduce absorption by 50–90% or more.
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
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.
1. Bushra R, Aslam N, Khan AY. Food-drug interactions. Oman Med J. 2011;26(2):77-83. doi:10.5001/omj.2011.21
2. Neuvonen PJ. Interactions with the absorption of tetracyclines. Drugs. 1976;11(1):45-54. doi: 10.2165/00003495-197611010-00004. PMID: 946598.
3. Shutter MC, Akhondi H. Tetracycline. [Updated 2023 Jun 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549905/
4. Yan A, Bryant EE. Quinolones. [Updated 2023 May 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557777/
Disclaimer: This information is for educational purposes only and does not replace professional medical advice.