Do GLP-1s Increase Bone and Tendon Injury Risk in Runners? Here’s What Doctors Want You to Know

GLP-1s, the shortened and now renowned name for glucagon-like peptide-1 receptor agonists, are a class of medications used to treat diabetes, as well as obesity. They act on the GLP-1 receptor in the body to slow gastric emptying (how fast your food moves through your body), as well as reduce “food noise” by acting on hunger hormones.These drugs have exploded in popularity in recent years with 11 percent of U.S. adults currently taking one for weight loss purposes, up from 3 percent in 2024, per a recent Gallup analysis.If you’re a runner considering losing weight via a GLP-1 or you’re already taking the meds, it’s important to consider how they might affect not just your weight or health, but also your performance—and injury risk.The good news is that the medication can have positive effects over time when it comes to injury risk thanks, simply, to the weight loss. Excess weight can increase risk of falling and bone fractures, says Wajahat Mehal, MD, director of the Yale Weight Loss Program. “You definitely benefit from the fact that as the weight comes off, there’s less impact [on your joints as you run],” he explains.Still, there’s been chatter online and in the research community about whether these drugs can inadvertently increase bone and tendon injury risk. And that is possible, just more indirectly rather than from the medication itself, says Yuval Pinto, MD, a family physician at Johns Hopkins Medicine, specializing in weight management.Even so, there are ways to mitigate this risk, and the benefit qualified candidates can get from GLP-1s outweighs any negatives, Mehal adds.Here’s how GLP-1s could indirectly increase injury risk for runners—and how to avoid it.How GLP-1s Affect Injury Risk in RunnersThe first way that these drugs could affect injury risk is via relatively fast and significant weight loss. “When someone loses a big amount of weight, the bone turnover and the mechanical loading of the skeleton can be jeopardized,” Pinto says. This means that bone breakdown may happen faster than bone formation.One mechanism for this is that weight loss means your bones take on a lighter load, so they adjust to the lighter physical stress by decreasing bone formation and increasing breakdown, according to one research review. Nutrient deficiencies and changes in hormones may also play a role.However, subjects in a 2024 study in JAMA who exercised in addition to taking liraglutide, a GLP-1, actually preserved bone health while losing weight, and the authors note that both aerobic and resistance exercise when eating fewer calories can counteract bone loss. Those who just took liraglutide saw a decrease in hip and lumbar spine bone mineral density.Similarly, a separate study out of UCLA Health, published in 2026, found that GLP-1s can reduce the risk of serious fractures for adults with type 2 diabetes.Pinto points out the subjects in the JAMA study lost an average of 10 percent body mass, a significant amount, and any adverse effects on bone mineral density were likely a result of the drug’s ability to suppress appetite. “If you eat less and run equally, there is a deficit here that could potentially harm the tendons and bones,” Pinto says. “Bone remodeling is metabolically very expensive and also it’s among the first budgets the body cuts.”If your body stops bone remodeling to save energy, but you keep running, that could mean bone is getting damaged faster than it’s getting replaced. And once the skeleton is damaged, everything that supports it, including tendons and ligaments, would also get damaged, Pinto says.Plus, in addition to simply taking in fewer calories when on a GLP-1, there’s a proportionate shrinking of nutrients like calcium, vitamin D, and protein, all of which help protect bones, tendons, and muscles, he adds.But, again, as long as someone is mindful of their calorie and nutrient intake, their risk shouldn’t go up, Pinto says.Mehal agrees, adding that it’s “perfectly safe” to run while taking a GLP-1 as directed, although performance could suffer during the active weight loss phase.“If for the last two months, every day you’ve been getting a few hundred calories less than your body needs, and then the day of the race or the run, similarly you’re under-caloried, then your performance is going to not be as good,” Mehal says, because you won’t have the energy you need to perform. (This is why you want to work with your doctor to balance running and nutrition, especially when you first start taking a GLP-1.)At the extreme end of this, Pinto says, is relative energy deficiencies in sport (RED-S), which can happen when underfueling becomes severe, prolonged, or recurrent enough to impair health or performance. “If not treated, and coupled with steady weight loss and muscle loss, this could lead to declined performance, recovery, disrupted sleep, mood change, and recurrent nagging injuries, like bone stress injuries,” he says, adding that it can also cause changes in libido and, for women, RED-S can be associated with menstrual issues.How to Avoid Injury While on GLP-1sAdjust Your Training During the Initial Weight Loss Phase The doctors point out that there’s a difference between casually running 20 miles a week and being a competitive runner training intensely for a marathon. The latter runner probably shouldn’t be training this way and on a GLP-1 while in the initial active weight loss phase, Mehal says.“These drugs [can] result in 15 to 20 percent weight loss and that occurs over six to nine months,” he says, which is when your appetite will be most suppressed and you may not be able to eat enough to support serious training.Once you go into maintenance mode: “It’s safe to train—even for a full marathon—while on GLP-1s as long as the rate of weight loss is reasonable, which is 0.5 pounds to 1 pound a week.” (And you’re following the below guidelines!)Talk to Your Doctor About Dosing Again, these drugs can help people lose weight quickly, but Mehal points out that for very active people, starting at a lower dose and increasing at a slower rate could be the way to go. So it’s important to mention your running routine to your doctor.“The fastest that you can increase the dose is every month, but I would encourage people who are doing a lot of active exercise to not increase it more than every two or three months,” Mehal says.If you take 12 months to get to your goal weight instead of six months, it’ll be less disruptive to your daily routine and you’ll feel less fatigued.Make Sure You’re Getting Enough Calories “The easy bottom line is that overall calories come first regardless of where they're coming from,” Pinto says, although it’s ideal, of course, to prioritize whole foods over ultraprocessed products.Talk to your prescriber about exactly how many calories you need based on your current weight, goal weight, and exercise routine.Then Consider Macros Pinto says to start with aiming to get between 1 and 1.5 grams of protein per kilogram of bodyweight per day distributed across three or four meals.“After protein, for runners, carbs are key,” he says, although needs can be more variable. While complex carbs are ideal, simple carbs can fit into a runner’s diet, too, particularly prerun.Maximize MicronutrientsCalcium and vitamin D in particular can help protect bones, Pinto says, pointing to an older study of female navy recruits that found that the micronutrients decreased the incidence of stress fractures.You can get the former in foods like kale and soybeans and the latter through fatty fish and egg yolks, for example.Talk to your provider about bloodwork before considering supplementation.Make Strength Training (and Good Sleep) a PriorityStrength training should be non-negotiable for anyone on a GLP-1, Pinto says. But it’s particularly important for runners to help strengthen bones and prevent injury.In combination with protein and good sleep (what Pinto calls the “holy triad”), lifting weights can help mitigate lean muscle loss when you’re in an energy deficit.On the flip side, “when you’re weak, when you don’t have enough balance, when you run for hours upon hours, your chances of harming your tendons is high,” Pinto says.Monitor for Symptoms of Overly Rapid Weight Loss If you notice symptoms like hair loss, poor recovery, disrupted sleep, mood changes, reduced libido, or recurrent nagging aches and pains while on a GLP-1, speak to your provider, Pinto says. Women should also report changes in their menstrual cycle.Keep Tabs on Muscle Loss Pinto recommends DEXA bone composition scans every couple of months while on a GLP-1 to keep tabs on lean body mass loss (e.g., muscle and bone) versus fat loss. He also recommends asking your doctor about blood tests, checking vitamin D, iron, and potentially certain hormones, like testosterone and thyroid hormones, which can all help paint a fuller picture of bone health.Adjust Your Training as NeededAt the end of the day, listening to your body is always the key. “Be aware of how your body is feeling,” Mehal says. “Even for casual runners, there may be some days they go out and they just don’t feel well or they don’t feel that they can run the distance that they’re used to running.” It’s okay to pull back or slow down, especially while acclimating to a new medication.