Here's what you should ask you doc before you fill that script.

If you've ever had strep throat or a UTI, you were probably handed a prescription for antibiotics and told to complete the full course (or else). But a new paper in the BMJ says it's time to start rethinking that advice.

By now, you've probably heard about this massive looming public health problem of antibiotic resistance. The idea: We're so quick to reach for medicine at the first sign of a sniffle that bacteria are actually learning how to resist the healing power of antibiotics. There's been a long-held belief by docs that if you don't complete a full course of antibiotics, you're allowing the bacteria a chance to mutate and become resistant to the drug. In fact, an analysis earlier this year by the World Health Organization found that among public health campaigns around the world, over half encourage people to finish an entire course of antibiotics, compared to just 27 percent that promote a strategy based on seeing how you feel throughout the course of treatment.

But in this new opinion paper, researchers across England say the need to finish a pill pack isn't actually based on any reliable science. "There is no evidence that completing a course of antibiotics, as compared to stopping early, increases the risk of antibiotic resistance," says study author Tim Peto, D.Phil., professor of infectious diseases at Oxford Biomedical Research Center.

What's the risk of taking more antibiotics than you need? Well, for one, Peto speculates that, opposite to the assumption of many docs, longer courses of treatment may actually promote the emergence of drug resistance. And a 2015 Dutch study found the same may be true for taking them too often: When people took multiple types of antibiotics over time (for different illnesses), this diversity enriched the genes associated with antibiotic resistance.

And there are other unpleasant side effects, too. We also know that some people experience side effects like antibiotic-associated diarrhea and even impaired gut health. That same Dutch study also found when people took a single, full course of antibiotics, their gut's microbiome was affected for up to a year. (Related: 6 Ways Your Microbiome Affects Your Health) One study even found that frequent use of antibiotics may increase your risk for type 2 diabetes.

"The optimal duration of antibiotic treatment is not yet known, but it is well-known that many people recover from infections with only a short duration of treatment," Peto adds. For example, certain infections-like tuberculosis-do require a longer course, he points out, but others, like pneumonia, can often be zapped with a shorter course.

More research is clearly needed, but until we have more hard science, you don't need to blindly follow their first recommendation. Talk to your doc about whether you *need* to take this course of antibiotics or if your system will clear this strain of bacteria on its own. If he or she tells you to take it, talk about whether you can stop before the end of the pack if you're feeling better, Peto advises.