Effects of Tirzepatide on Erythropoiesis in People with Obesity: An Individual Patient Data Meta-analysis of the SURMOUNT Trials

Obesity means having too much body fat. It can cause serious health problems like diabetes (a condition where the body's blood sugar is too high due to problems regulating a hormone called insulin), heart disease, and trouble sleeping. More than 650 million people around the world live with obesity. A new medicine called tirzepatide is taken once a week by a small injection under the skin. It sends “fullness” signals from the digestive system to the brain, so people feel less hungry, eat less food, and lose weight. In large studies named SURMOUNT-1, -2, and -3, tirzepatide helped many people lose a substantial amount of weight without surgery.

Weight-loss surgery has been the main way to achieve significant weight reduction, but it can sometimes lead to side effects like anemia. Anemia happens when there is not enough hemoglobin—the part of red blood cells that carries oxygen throughout the body. Low hemoglobin can cause tiredness and weakness and may be related to poor absorption of nutrients like iron after surgery. Because tirzepatide can cause similar weight loss without surgery, researchers are studying whether it could also change hemoglobin levels or have other effects on blood health. This matters because both low and very high hemoglobin have been linked to a higher risk of heart disease and early death.

In this research, I will study data from three large clinical trials to find out whether tirzepatide changes hemoglobin levels in people with obesity. People in these studies were randomly assigned to receive either tirzepatide or a placebo (a dummy treatment with no active medicine), and their blood tests—including hemoglobin—were measured before and during treatment. I will combine and analyze the individual data from all three trials to look for patterns over time. I will also explore whether changes in hemoglobin differ by age, sex, body-mass index (BMI), type 2 diabetes status, or other health conditions. This study will help doctors understand the safety profile of tirzepatide for blood health and whether there are any possible long-term effects to consider. The findings could improve care for millions of people with obesity who are considering new treatments.