In a sweeping analysis of more than 400,000 Reddit posts, researchers have revealed some little-known GLP-1 side effects.

GLP-1 receptor agonists — such as semaglutide (Ozempic and Wegovy), and tirzepatide (Mounjaro and Zepbound) — have been most commonly associated with gastrointestinal side effects, such as nausea, vomiting, diarrhea and constipation.

A new study published in Nature Health, however, uncovered some overlooked effects.

SHOULD YOU MICRODOSE OZEMPIC? EXPERTS ARE SPLIT ON RISKS VS BENEFITS

University of Pennsylvania researchers used artificial intelligence to analyze more than five years of Reddit posts from more than 67,000 people taking the popular drugs for diabetes or weight loss.

While clinical trials are still the “gold standard,” the researchers noted that Reddit community feedback reflects a different population.

“People often use medications differently than they’re prescribed, so it’s also important to look at real-world usage, which can diverge from usage in a clinical trial,” lead researcher Neil Sehgal, a PhD student at the University of Pennsylvania, told Fox News Digital. “So there are many possible reasons we’re seeing signals that the trials may have missed.”

Overlooked effects

Nearly half of the users reported one or more side effects. The most common were nausea, vomiting and constipation, which aligned with what clinical trials found, according to Sehgal.

“We’re almost certainly capturing a skewed slice of the full picture.”

“We did notice a few side effects that have not previously been reported for these drugs,” he told Fox News Digital. 

“For example, about 4% of users who described side effects reported menstrual irregularities. Other Redditors described unusual temperature-related symptoms, like chills or hot flashes.”

OBESITY EXPERT REVEALS THE BEST WAY TO DECIDE IF GLP-1S ARE RIGHT FOR YOU

Nearly 13% of users also experienced psychiatric symptoms, such as anxiety, depression and insomnia. More than 5% also complained of abdominal pain, acid reflux, headache and dizziness.

“Fatigue was also the second most commonly reported symptom overall, but has met relatively few reporting thresholds in existing trials,” Seghal noted. “This gap between what patients are self-reporting online and what gets captured in trials is really what motivated this whole line of work.”

Clinical context

Dr. Sue Decotiis, a New York City-based board-certified weight-loss physician, noted that many of the reported symptoms, such as disorientation and fatigue, are most likely due to dehydration and hypoglycemia (low blood sugar).

“Patients should be carefully monitored using a structured protocol that ensures proper nutrition and adequate hydration, ideally under the direct supervision of a physician experienced in metabolism and weight loss,” Decotiis, who was not involved in the study, told Fox News Digital. 

“Additionally, body composition analysis can help identify issues such as muscle loss, excessive water loss or insufficient fat loss.”

CLICK HERE TO SIGN UP FOR OUR HEALTH NEWSLETTER

A significant concern, according to the doctor, is that many individuals are accessing these medications through online platforms or without receiving appropriate medical care. 

“In my experience treating thousands of patients with various GLP-1 medications, complications are rare and typically occur only when patients are noncompliant,” she added.

Study limitations

As the data came from Reddit users, who tend to be younger, primarily male and mostly based in the U.S., it may not represent everyone taking these medications, the researchers noted.

“And even within Reddit, the people who post about their side effects are probably not typical of everyone on the medication,” Sehgal said. “If you had a good experience, you’re less likely to be writing about it online. So we’re almost certainly capturing a skewed slice of the full picture.”

The researchers also noted that the study can’t prove the drug caused the reported symptoms.

CLICK HERE FOR MORE HEALTH STORIES

“To be clear, we can’t say for certain whether these drugs are causing menstrual irregularities,” Sehgal said. “Patients on Reddit aren’t going to self-report every symptom they have, and they may also report things that aren’t actually linked to the medications. So it’s important to treat this as hypothesis-generating signals and do more research.”

The study also didn’t include GLP-1 dosage, duration of the medication and symptoms, or other health conditions the users experienced. There is also the chance that the AI tools misunderstood meanings or context, the researchers noted.

TEST YOURSELF WITH OUR LATEST LIFESTYLE QUIZ

The results must be confirmed with more rigorous research, Sehgal said. “That’s how we’ll get real answers about prevalence and causality, which social media data alone can’t provide.” 

CLICK HERE TO DOWNLOAD THE FOX NEWS APP

“These are signals, not conclusions – but I do think it’s always worth talking to your doctor about anything unexpected you’re experiencing while on a new medication, even if you’re not sure if it’s related,” he advised. “So if something feels off, say something.”

Anemia, a common blood disorder, may be a major risk factor for developing cancer.

That’s according to new research from Sweden, which sought to discover whether newly developed anemia is an early warning sign of cancer or death from any cause.

The study, published in BMJ Journals, looked at registry data from more than 380,000 Swedish adults – half were people with new-onset anemia and the other half were the same age and gender, but did not have anemia.

CLICK HERE TO DOWNLOAD THE FOX NEWS APP

All participants were over 18 years old and cancer-free at the start of the study.

The results showed that people with incident anemia – new cases occurring over a specific period – had a significantly higher chance of being diagnosed with cancer, especially in the first three months, according to a press release. This included 6.2% of men and 2.8% of women.

Individuals with anemia also had a much higher chance of death during the 18-month follow-up.

Specific types of anemia were individually linked to disease progression and mortality, the researchers discovered.

CLICK HERE FOR MORE HEALTH STORIES

Microcytic anemia – where the red blood cells are smaller than normal – was more frequently linked to cancer, especially types of disease that impact the digestive system and the blood.

Macrocytic anemia, a type of anemia where the red blood cells are larger than normal, was more strongly linked to overall mortality than cancer.

The researchers concluded in the study that new-onset anemia is a “strong and sustained risk marker” for both incident cancer and all-cause mortality.

CLICK HERE TO SIGN UP FOR OUR HEALTH NEWSLETTER

Lead study author Elinor Nemlander, researcher at the Department of Neurobiology, Care Sciences and Society at the Karolinska Institutet, commented on the findings in a press release from the Swedish medical university.

“We found that both the risk of cancer and the risk of death are highest during the first months after anemia is detected, but that the increased risk persists later during follow-up as well,” she said. “Our findings suggest that anemia may be a sign of underlying disease rather than a condition in its own right.”

Speaking with Fox News Digital, Nemlander noted that measures like red blood cell size are already “routinely available” in primary care, and that the study highlights how this existing data can be used to identify early risk.

“At the same time, the elevated risks persist over time, underscoring the need for structured follow-up and clear plans for continued evaluation, even when cancer is not initially identified,” she said.

TEST YOURSELF WITH OUR LATEST LIFESTYLE QUIZ

As the study was observational, it shows an association, but does not prove that anemia causes cancer or death.

The research also did not measure for all causes of anemia, including alcohol use, malnutrition, chronic liver disease, inflammatory conditions and gynecological blood loss.

“Some of the results may also be influenced by who gets tested, underlying illnesses and differences in how anemia is evaluated in different healthcare settings,” Nemlander added.

An increasing number of patients are requesting “unvaccinated” blood for transfusions, which can delay care and pose risks to patients’ health, experts warn.

There is no evidence that unvaccinated blood presents any safety benefit, according to a new study published in the journal Transfusion.

There is currently no process for checking whether donated blood comes from vaccinated or unvaccinated donors, experts say.

CANCER SURVIVAL APPEARS TO DOUBLE WITH COMMON VACCINE, RESEARCHERS SAY

Vanderbilt University in Tennessee, which conducted the research, received 15 requests for unvaccinated blood between Jan. 1, 2024, and Dec. 31, 2025. The median age of patients was 17 years old and more than half were children, the university reported.

Thirteen of the patients received blood donated specifically for them by family members, which is known as “direct donation.” This can be risky, because most direct donors are giving blood for the first time, and their donations are more likely to contain “potentially harmful pathogens,” the authors noted. 

“Despite being framed as ‘safer,’ directed donations may paradoxically increase risk.”

COVID VACCINE UNDER NEW SCRUTINY AFTER STUDIES REVEAL POSSIBLE HEALTH RISKS

Among the studied patient group, two became much sicker after refusing a standard blood transfusion. 

One patient developed anemia, a condition where the body lacks enough healthy red blood cells to carry adequate oxygen. The other developed hemodynamic shock, a serious condition in which there is insufficient blood flow and oxygen to the body’s tissues, potentially leading to organ failure.

“Despite being framed as ‘safer,’ directed donations may paradoxically increase risk.”

Requests for unvaccinated blood spiked after the approval of COVID-19 vaccines, posing a “recurring challenge for transfusion services and clinicians,” the researchers stated.

“These requests were associated with care delays, escalation and inefficiencies,” they indicated.

FAMILY PLEADS FOR HELP AS TEEN FACES LIFE-THREATENING BONE MARROW FAILURE

The researchers recommend that health systems create standardized policies to handle these types of requests.

“Regulatory and professional organizations have opposed these non-evidence-based policies, emphasizing that blood centers do not record or convey donor COVID-19 vaccination status and that evidence demonstrates transfusion from vaccinated donors poses no unique risk.”

The Vanderbilt study had some limitations, the researchers noted. It looked at a small number of cases and only included situations where special blood donations made it to the blood bank, so it doesn’t show how often people made this request overall. 

CLICK HERE FOR MORE HEALTH STORIES

It also didn’t include cases where concerns were resolved through conversations with doctors or ethics teams, the team noted.

As this was an observational study and not a controlled experiment, it only showed an association and could not prove that refusing standard blood directly caused any specific patient outcomes.

CLICK HERE TO SIGN UP FOR OUR HEALTH NEWSLETTER

Several states have introduced proposals aimed at allowing patients to receive blood specifically from donors who have not received COVID-19 vaccines.

In Oklahoma, one such proposal called for the creation of a state-run blood bank dedicated to collecting and distributing blood from unvaccinated donors. Despite these efforts, none of the measures have been enacted into law.

Dr. Marc Siegel, Fox News senior medical analyst, was not involved in the research, but said these types of requests are “part of an ongoing fear culture.”

“It is also very difficult to test for, because the antibodies may be positive from COVID itself as well as the vaccine, and it can be difficult to tell the difference,” he told Fox News Digital.

CLICK HERE TO DOWNLOAD THE FOX NEWS APP

The notion that receiving blood from someone who had the vaccine would be harmful is not based on any scientific studies, the doctor reiterated.

“If people want to group up to get blood from other unvaccinated people, I respect that choice, though it will be expensive and will limit options,” Siegel added.

Diane Calmus, vice president of government affairs for America’s Blood Centers in Washington, D.C., said that requests for direct donations are “exceedingly rare” – representing about 0.06% of the U.S. blood supply.

“Requests for unvaccinated blood are something we’ve seen wax and wane since the introduction of the COVID vaccine,” Calmus, who also was not involved in the Vanderbilt study, told Fox News Digital. “The challenge is that there’s no way to tell whether someone’s blood has been vaccinated – there’s no test that exists.”

TEST YOURSELF WITH OUR LATEST LIFESTYLE QUIZ

Any situation where someone requires a blood transfusion is most likely a “very scary time,” she noted.

“Family members want to be cautious, and this is why it’s so important that people talk to a transfusion medicine-trained doctor,” the expert advised. “These are physicians who have a specialty in blood transfusions … and who can answer those questions that any individual will have.”

Calmus pointed out that it takes some time to facilitate a direct donation, and that there is a specific process in place. 

“Blood has to be prescribed. You can’t just show up at the blood center and say, ‘I would like my sister to donate for me,’” she said. “There needs to be a prescription. It needs to go through the hospital … they need to make sure it is the right blood for the right patient.”

“We need people – vaccinated or not vaccinated – to show up and donate blood, because it is the blood on the shelves that saves lives.”

Calmus emphasized that the U.S. blood supply is “meticulously tracked,” and that there have been no indications of a lack of safety. She also stressed the ongoing need for blood donors.

“We need people – vaccinated or not vaccinated – to show up and donate blood, because it is the blood on the shelves that saves lives.”

Fox News Digital reached out to the Vanderbilt researchers for comment.