Antibiotics can cure. They kill infectious bacteria and save lives. Type 2 diabetes is a chronic disease. It shortens lives. But older men and women generally have to be extra careful when it comes to antibiotics, and now there is disturbing evidence that the cure may be contributing to the disease—in other words, certain antibiotics may increase the risk of developing diabetes. The connection is the ecosystem of bacteria in our gut that scientists call the microbiome. It affects digestion and immunity, and an unhealthy microbiome has been linked to diseases as diverse as obesity, certain cancers, inflammatory bowel disease, rheumatoid arthritis, and diabetes.

Several studies have shown that type 2 diabetes, the kind that affects most people, is more common in people who have microbiomes with altered or low bacteria diversity. What we eat and drink changes the composition of the bacteria, and so can the medication we take, especially antibiotics. Penicillin, the original wonder drug, saved soldiers from battlefield infections in World War II and later revolutionized medicine by curing once-fatal infections. But antibiotics by their very nature disturb the microbiome by killing bacteria, including beneficial bacteria in the gut. Now, the newest research finds an association between the repeated use of certain antibiotics and the diabetes epidemic that affects thirty million Americans…and counting.


In the latest study, researchers had access to nearly complete medical records of almost ten million people living in the United Kingdom. The records included medical diagnoses, tests and procedures, prescription medications, and lifestyle factors, including smoking and drinking history. The research team identified 208,002 people who were diagnosed with diabetes (either type 1 or 2).


Each case was matched with four controls, people of the same age and sex who did not have diabetes. In all, the study included more than one million men and women, with an average age of sixty. Looking deeper into the medical records of the participants, the researchers searched for prescriptions for several different antibiotics, including, yes, penicillin, still the most popular choice. They excluded antibiotics prescribed in the year before a diabetes diagnosis, since many of these patients may have had undiagnosed diabetes already. They adjusted statistically for many variables, including smoking, high cholesterol, obesity, heart disease, skin and respiratory infections, and previous blood sugar measurement. The results:

  • In most cases, a single course of antibiotics was not associated with any increased risk for diabetes, compared with taking no antibiotics at all.
  • The exception was a class of antibiotics called cephalosporins, broadspectrum antibiotics often prescribed for strep throat and urinary tract infections (UTIs). Even taking a single course of these antibiotics was associated with a 9 percent increase in type 2 diabetes risk.
  • For the antibiotics linked with type 2 diabetes, the more courses people took in any one year, the greater the risk. Taking two to five courses of penicillin in a single year was linked to an 8 percent increase in diabetes risk, for example, while taking more than five courses was linked to a raised risk of 23 percent. Similarly, taking two to five courses of quinolones, prescribed for skin and respiratory infections as well as UTIs, was linked to a 15 percent increase in diabetes risk, while taking more than five courses raised risk 37 percent.
  • Tetracyclines were associated with a raised type 2 diabetes risk only in people who took them for five or more courses in a year.
  • Nitroimidazoles, prescribed for vaginal infections as well as skin infections such as rosacea, were not associated with increased diabetes risk when taken at any frequency.
  • Neither antiviral nor antifungal medications were linked with diabetes risk.
  • While there appeared to be an association between some antibiotics and type 1 diabetes, an autoimmune condition, for some antibiotics, the results were inconclusive.


This study, while big and statistically powerful, doesn’t tell us whether using antibiotics actually cause diabetes. That’s because it’s observational. It looks back and draws connections. A prospective study would assign one group of people to take antibiotics whether they need them or not, deny them to another group, and follow them for years to see who gets diabetes. For practical and ethical reasons, of course, that’s impossible. So it’s possible that people who would go on to develop diabetes even years later are more prone to infections and so would need more antibiotics. On the other side, prospective animal studies have shown that antibiotics promote the growth of bacteria that promote diabetes. Because diabetes is so common and such a damaging disease, researchers are looking for other ways to tease out whether and how antibiotics contribute to diabetes. You don’t have to wait to do the right thing though.

These wonder drugs have been overused, both for human medicine and animal livestock, and many are losing their effectiveness due to rising antibiotic resistance, a scary prospect. Using antibiotics only when they are really needed not only protects your own health but helps keep these drugs effective when they are really needed. By all means, take an antibiotic if it’s the right treatment. But there are already many good reasons to avoid antibiotics if possible, and the truth is, they are often prescribed for health conditions for which they can’t possibly work. Antibiotics kill bacteria, so they won’t help with, say, the common cold, which is caused by a virus. Most sinus infections, even those caused by bacterial infections, don’t require antibiotics either. In many cases, doctors prescribe antibiotics when they’re not needed because a patient insists on it for almost any sort of infection or even suspected infection. Don’t be that patient!

Certain Statins Are Linked to Diabetes

Has your doctor put you on cholesterol-lowering statin medication or suggested that it’s time to start? If so, you probably know that statins can have some very serious side effects, such as muscle aches, liver problems, and perhaps impaired memory. But you may not have heard that the medication can increase your risk for developing a very common and potentially deadly disease—diabetes. Now, thanks to a major recent study, we’ve learned that all statins are not created equal when it comes to diabetes risk. As it turns out, some are significantly riskier than others. Which type are you taking?


Statin drugs reduce blood cholesterol levels by interfering with an enzyme that helps the liver make cholesterol. However, different types of statins work in slightly different ways, and their effects on the body vary somewhat. Earlier studies suggested that statins in general made people more likely to get diabetes, but that one type, pravastatin, made people less likely to get diabetes. So for the recent study, researchers set out to determine more specifically how the most commonly used types of statins affected the risk for diabetes relative to each other. With access to health and pharmacy records of 1.5 million older Canadians, researchers identified 471,250 people age sixty-six and up who did not have diabetes when they first started taking statins.

Then they followed each statin user for up to five years to see which ones got diabetes. (Though this study took place in Canada, the same statin drugs are prescribed in the United States.) An earlier study suggested that patients taking pravastatin had a lower risk for diabetes compared with people taking a placebo. For that reason, in the new study, the researchers used pravastatin as the basis of comparison in gauging the diabetes risk associated with five other types of statins. After adjustments were made for various other diabetes risk factors (age, sex, health status, other medication use), here’s how each drug fared relative to pravastatin:

  • Atorvastatin, which accounted for more than half of all new statin prescriptions, was associated with a 22 percent increase in diabetes risk.
  • Rosuvastatin was associated with an 18 percent increase in diabetes risk. However, the researchers noted that this risk may be dose-dependent, meaning present at higher dosages but not at lower dosages.
  • Simvastatin was associated with a 10 percent increase in diabetes risk.
  • Both lovastatin and fluvastatin were comparable to pravastatin.


There are several possible explanations for why patients taking certain statins are more prone to develop diabetes. Some statins may cause damage to beta cells, which are responsible for storing and secreting insulin, and/or these statins may interfere with the process that transports glucose from the blood through the cell membrane and into the body’s cells. As for why pravastatin might reduce diabetes risk, animal studies have suggested that it improves cells’ sensitivity to insulin. Lovastatin and fluvastatin may have similar beneficial effects on insulin sensitivity.

Bottom line: If you are taking or have been advised to take one of the statins associated with increased risk for diabetes (atorvastatin, rosuvastatin, simvastatin), talk with your doctor about the diet and lifestyle changes that could lower your cholesterol and perhaps reduce your need for the medication. Also, discuss whether it’s appropriate to consider switching to pravastatin (or perhaps lovastatin or fluvastatin), particularly if you have other risk factors for type 2 diabetes, such as excess weight, high blood pressure, high triglycerides, a history of gestational diabetes or polycystic ovary syndrome, or a family history of diabetes.

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