Millions of people taking blood pressure medications are being advised to pay close attention to what they drink, as certain beverages may reduce the effectiveness of their prescriptions or even trigger harmful side effects. Medications such as ACE inhibitors, beta-blockers, and diuretics are essential for managing high blood pressure, a condition affecting over 16 million people in the UK, many of whom are unaware they have it.

Experts at Health, however, a publication founded in 1981 with a medical advisory board of 70 board-certified physicians and healthcare professionals, have warned that some seemingly harmless drinks can interfere with how these medications work.

1. Some fruit juices

Grapefruit juice is one of the most well-known culprits. According to Sabrina Islam, MD, MPH, a cardiologist at Temple Health and an associate professor of medicine at the Lewis Katz School of Medicine at Temple University, it can block an enzyme called CYP3A4, which helps break down many blood pressure medications.

Other fruit juices, such as apple or orange juice, may also interfere with the way the body absorbs and metabolises some blood pressure medications, explained Dr David Maron, a cardiologist at Stanford Medicine’s Preventive Cardiology Clinic.

2. Alcohol

Alcohol consumption can significantly amplify the effects of blood pressure medications, particularly beta-blockers, ACE inhibitors, and alpha-blockers. This interaction can cause blood pressure to drop too low, resulting in dangerous dizziness, fainting, rapid heartbeat, and falls. On top of that, alcohol itself can raise blood pressure, reducing the benefits of medication. Dr Maron advised no more than one drink per day for women and two for men.

3. Caffeinated beverages

Caffeine increases blood pressure when it enters your bloodstream, and it can also diminish the effectiveness of some medications, particularly beta-blockers and diuretics. People with hypertension should be cautious with caffeine, even if they are not taking these medications. Dr Maron recommends keeping caffeine intake below 400 milligrams per day. 

4. Licorice tea

Liquorice tea contains glycyrrhizic acid, which can significantly raise blood pressure and cause dangerous interactions with antihypertensive medications, even if consumed in small amounts. It acts by causing sodium retention and potassium loss, which reduces the effectiveness of blood pressure drugs. 

5. Herbal teas and supplements

Certain herbal products, such as St. John’s wort, ginseng, ephedra, yohimbine, liquorice root, and high-dose green tea extracts, may interfere with how the body processes blood pressure drugs. These interactions can reduce the effectiveness of medications or trigger side effects such as dizziness, irregular heart rhythms, or low potassium levels.

6. High-sodium vegetable juices 

While some vegetable juices can help lower blood pressure, such as celery, beetroot, or leafy green blends, those that are high in sodium can actually counteract blood pressure medications, particularly diuretics, ACE inhibitors, and ARBs, potentially leading to increased blood pressure, swelling, and reduced drug effectiveness. 

According to Blood Pressure UK, high blood pressure is the third largest risk factor for disease in the UK, after smoking and poor diet.

Experts have warned that patients taking blood pressure medications should speak with their healthcare provider before consuming these beverages to ensure their treatment remains safe and effective.