If you’ve had a bacterial infection in the last few years, whether a urinary tract infection (UTI), strep throat, ear infection or any other bacterial illness, you might’ve been prescribed antibiotic medications. And, if you were, you’ve likely heard the following instructions: Finish all of your antibiotic pills. Maybe you heard it from your provider or the pharmacist who dispenses your medications, perhaps you noticed it written in all caps and bolded on the bottle, or maybe a loving caregiver told you to take them all. Well, now you’re also hearing it from your friendly health writer, too. Completing your antibiotic course is essential for your current infection, overall health, and even public health concerns.

What are antibiotics, anyway

“Antibiotics do one thing and one thing only: kill bacteria,” says Linda Yancey, MD, Infectious Disease Specialist, Memorial Hermann Health System in Houston. Specific antibiotics eliminate certain bacteria they are made to kill with different physiological mechanisms. For example, nitrofurantoin (Macrobid) is a commonly used antibiotic for UTIs because it targets bacteria in and around the urinary tract.

Dr. Yancey stresses that researchers design dosage amounts and schedules for years to make them effective. There’s a reason for every number you see on that clear orange bottle. The medications need time to destroy the bacteria in your body. Not finishing the course of pills you’re prescribed simply because you feel better or your symptoms subsided is not good for your overall health.

How do they impact your health

When you take too short of an antibacterial course, it can have two effects. First, it is possible that your infection won’t be entirely obliterated—even if you start to feel better. If you take enough of your antibiotics to reduce, say, 70 percent of the bacterium in your body, sure, your symptoms might subside. But the 30 percent of bacteria that are left can increase in a few days or weeks, Dr. Yancey explains.

Not only can they replicate—but bacteria can also change, and like all living things, they can grow more robust to survive. If you introduce a specific antibiotic into your system to fight these invaders—you want them to kill them completely, Dr. Yancey says. Introducing medicine into your system to only kill a portion of the infection can actually offer bacteria a chance to replicate in a way that can fight against the medication. This means that there’s a chance that the infection could resist your medicine and be harder to kill when you start a medicine again.

What are the bigger picture effects

Believe it or not, this also has broader public health concerns. When contagious infections evolve as a result of an unfinished medication or ineffective treatment (which also happens), they can spread. From a public health perspective, this is dangerous. You don’t want an invader to get stronger, more contagious, and resistant to the treatment that is supposed to kill it. This is how illnesses become more potent and harder to treat on a broader, societal level.

The best way to combat this and protect yourself from antibiotic resistance is to follow your provider’s instructions and check the details on your medication instructions if you forget. And, as Dr. Yancey stresses, make sure you remember to continue taking your meds even after you start to feel better.

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