Look in most medicine cabinets and you’ll find a bottle of aspirin. It’s a common painkiller and anti-inflammatory. Added to that, around half of all older adults take a low-dose of aspirin every day. This regimen is often recommended by medical professionals because of aspirin’s value as a blood-thinner, which can help to prevent heart attacks and strokes.

But there are also risks. For one, aspirin can cause unwanted internal bleeding, particularly in the gastrointestinal track. Now a new study points to another red flag: Long-term, regular use of low-dose aspirin may increase the risk of developing anemia.

Anemia happens when we don’t have enough red blood cells. Red blood cells carry crucial oxygen via hemoglobin, which is a protein that contains iron. When our red blood cell count is low, there’s less oxygen getting to organs and tissues. This can result in fatigue, rapid heartbeat, shortness of breath or light-headedness. Other common causes of anemia are a deficiency of vitamin B12, folic acid or iron — as well as illnesses such as cancer, kidney disease, ulcerative arthritis or rheumatoid arthritis.

The risk of developing anemia in the group taking aspirin was 20 percent higher than those participants taking the placebo.

To understand how taking daily low dose aspirin affected older people, Australian researchers from Monash University analyzed existing data from a trial study called “ASPRirin in Reducing Events in the Elderly” or ASPREE. This is a long-term, multi-center study specifically focused on aspirin and its relationship to health in older adults. In this case, the researchers wanted to understand the relationship between taking low-dose aspirin and the risk of anemia.

They followed over 18,100 adults from Australia and the U.S. who were age 70 and older for 4.5 years. All were healthy at the start of their study. Half of them took a daily low (100 mg) dose of aspirin; the other half were given a placebo, a treatment that has no active properties, such as a sugar pill.

The risk of developing anemia was 20 percent higher in the group taking aspirin than among those taking the placebo. That’s not all. They also found that hemoglobin levels declined faster and ferritin levels were also reduced in the aspirin-taking group. Ferritin is a blood protein that contains iron. The good news is that the reduced hemoglobin and ferritin levels weren’t the result of major bleeding.

So, what do the findings mean? “This study gives a clearer picture of the additional risk of becoming anemic with aspirin use and the impact is likely to be greater in older adults with underlying diseases, such as kidney disease,” Zoe McQuilten, lead author of the study and Associate Professor (Research), Acute & Critical Care at Monash University, said in a press release.

The researchers suggest their study’s findings indicate that health professionals might consider monitoring symptoms of anemia more frequently in those healthy older adults who are taking aspirin.

Iron helps boost hemoglobin. There are ways to get more of this mineral through your diet. The following eight foods that are especially rich in iron:

  • Shellfish (clams, oysters, mussels)
  • Spinach
  • Organ meats such as liver
  • Legumes (beans, lentils, chickpeas)
  • Red meat
  • Dark chocolate
  • Pumpkin seeds
  • Broccoli

The study is published in Annals of Internal Medicine.