When a prescription label reads, “Take one tablet by mouth once daily,” does that mean every day at 8 a.m.? Whenever you eat lunch? Whatever time works best for you?

It depends, say the experts at Harvard Health. For maximum effectiveness, certain medications should be taken at specific times of the day. This approach is called chronotherapy and research shows that when you take your prescription drugs can not only boost their efficacy, but also prevent potentially unpleasant side effects. Here are some classes of drugs and recommendations on when to take them. Always check with your own healthcare practitioner or pharmacist to ensure personal safety.

• Blood pressure. Timing depends on the type of medication you are taking, says Dr. Junwei Liu, an internal medicine physician at Aurora Wilkinson Medical Center in Summit, Wisconsin. In general, if you take diuretic pills to control blood pressure, take them early in the day. Diuretics tend to make you urinate more frequently, so you don’t want to disrupt your sleep by taking these medications at night. Taking other types of blood pressure pills at night such as ACE inhibitors and ARBs may reduce your risk of stroke or heart attack.

• Thyroid. It’s best to take thyroid medication first thing in the morning, says Liu. Since thyroid medications can interact with other meds, always take them on an empty stomach with no other medicines.

• Osteoporosis. Bisphosphonates, prescribed to prevent bone loss in people with osteoporosis, are better taken in the morning says Joshua Gagne, an associate professor of medicine at the Harvard T. H. Chan School of Public Health. “Take them first thing in the morning with a large glass of plain water, at least 30 minutes before eating or drinking anything or before taking any other medications,” he says.

• Cholesterol. If you take a cholesterol-lowering statin drug, it is best to take it at night, says Liu. Statin medications work by slowing your body’s process of making cholesterol, so when you haven’t eaten in a while or are sleeping, cholesterol production ramps up.

• Asthma. Asthma attacks occur 50 to 100 times more often between 4 a.m. and 6 a.m. than any other time of the day. Four in 10 people wake up every night with difficulty breathing. Take your oral medication mid-afternoon, and if you are using an inhaled steroid, the best time is late afternoon. This gives the medication time to reduce inflammation and relax airways before bedtime.

Dr. Liu also suggests taking your medications at the same time every day so that it is easier to remember when to take them.