Research by scientists indicates that certain types of antibiotics may lose effectiveness when taken with milk, particularly those used to treat bacterial infections.
Oral antibiotics—whether in tablet or liquid form—need to be absorbed into the bloodstream to work effectively. However, when consumed alongside dairy products such as milk, cheese, or yogurt, some antibiotics are not absorbed as expected.
According to studies, the absorption of an antibiotic called demeclocycline (brand name Declomycin) into the bloodstream can decrease by up to 83% when taken with milk, compared to when taken with water or a non-dairy meal. Demeclocycline is used to treat respiratory infections, such as pneumonia.
Research shows that drinking milk before taking antibiotics may reduce the effectiveness of the medication. (Image: UniversalImagesGroup/Getty).
A study published in the European Journal of Pharmacology found that when the prostate cancer medication estramustine (brand name Emcyt) is taken with milk, it forms a complex with calcium, making it harder for the body to absorb the drug.
Another study published in the Acta Pharmacologica et Toxicologica revealed that the drug sotalol (brand name Betapace), used to treat irregular heart rhythms, also interacts with calcium. This combination reduces the absorption and effectiveness of the drug when taken with milk.
Furthermore, research indicates that when ciprofloxacin is taken with milk, drug levels in the bloodstream can decrease by about 30% to 36% compared to when taken with water. This antibiotic is used to treat a range of conditions, from pneumonia to gonorrhea.
There is less data regarding the impact of other dairy products, but studies generally indicate that they also reduce antibiotic levels in the bloodstream.
The interference of milk with the absorption of these medications is attributed to its high content of calcium and magnesium ions, referred to as “ions.” These ions can bind with certain antibiotics, forming an “insoluble compound.” According to Anastasiya Shor, an assistant professor at Touro College of Pharmacy in New York, in an email to Live Science, insoluble compounds do not dissolve in water, and if a drug cannot dissolve in the fluid within the intestines, it cannot be absorbed into the bloodstream.
When calcium and magnesium ions are present in the intestines, they effectively trap antibiotic molecules there. Consequently, the amount of antibiotic entering the bloodstream significantly decreases, reducing the medication’s effectiveness throughout the body.
This interaction with dairy products occurs only with certain types of antibiotics, particularly those belonging to two groups: tetracyclines and fluoroquinolones. It does not affect all antibiotics.
“To ensure antibiotics work as intended, patients should take their medication 2 hours before or 6 hours after consuming dairy products,” Shor advises. “This minimizes the interaction between calcium and antibiotics in the digestive tract, ensuring that patients receive the maximum benefit from their medication.”
