According to HMSA claims data, the average person in Hawaii fills 10 prescriptions per year — and seniors fill three times as many. Medicine helps keep us healthy, saves lives and curbs pandemics, but when medicines aren’t taken as directed or are combined in unsafe ways, they can have harmful effects.

To ensure you’re getting the most benefit from your medicine, talk to your doctor and pharmacist and carefully read the instructions that come with the medicine. Pharmacies have computer systems that check your prescriptions for possible interactions with other medicines you take, but they don’t account for over-the-counter medicines or herbal supplements.

Keeping your doctor and pharmacist informed is especially important for patients who take many medicines or supplements and those with chronic conditions or weakened immune systems. If you see several different doctors, be sure to let all of them know about all the medicines you are taking.

Medicine is broken down in the body either by the liver or the kidneys. Medicines broken down by the liver are more likely to have harmful interactions with other medicines.

Sometimes medicine interactions occur because people are unaware of the ingredients in their medicine. For example, it’s not uncommon for people to take both cold medicine and Tylenol at the same time, not realizing their cold medicine already contains acetaminophen (Tylenol’s active ingredient). Large doses of acetaminophen can cause liver damage, so taking only the appropriate dosage is important.

Sometimes patients unknowingly take duplicate medicines. Generic drugs often add to this confusion.

Food can affect the safety and effectiveness of medicine. An interaction that surprised the medical community several decades ago was the combination of statins, or cholesterol-lowering medicines, with grapefruit. A compound in grapefruit interacts with liver enzymes that break down statins. When the statins aren’t broken down properly, severe kidney and muscle damage can occur.

Your diet can also affect how your medicine performs. I once witnessed a man on blood-thinning medicine. His lab results showed his medicine was becoming less effective, so I asked whether he had changed his diet. The only thing he started doing differently, he said, was drinking green tea several times a day. It turned out that vitamin K in the tea was interacting with his blood-thinning medicine.

Senior citizens are especially prone to medicine interactions because they typically take a lot of medicines (five prescription drugs at the same time, on average). Age-related bodily changes, such as decreased liver function, can also make seniors more sensitive to certain medicines.

Medicare offers a no-cost program called Medication Therapy Management to eligible seniors that allows them to meet with a pharmacist to discuss their medicines. The pharmacist can help identify dangerous medicine interactions and might be able to help lower their prescription drug costs. Any changes to their therapy are discussed with and approved by their doctor. Seniors will receive a letter in the mail if they become eligible for this service.

Even though medicine interactions can be dangerous, it’s important to remember that medicine is generally helpful. You shouldn’t stop or avoid taking a medicine just because of possible interactions without talking to your doctor first. Always keep your doctor informed about all of the prescription and over-the-counter medicines, vitamins and herbal supplements you take.

And while generic drugs are a safe, affordable alternative to name-brand medicines, be sure you understand their function, to help prevent duplicating a medicine. If you are experiencing side effects or have questions or concerns about your medicines, discuss them with your doctor or pharmacist. Your doctor may be able to change your dosage or suggest a similar medicine to reduce any side effects.