Semaglutide begun in old age extended median lifespan about 12 percent in female mice, the only sex tested

A study published in Nature on September 2, 2026, reports that female mice given semaglutide starting late in life lived longer than untreated mice and performed better on tests of memory, movement and blood sugar control. The work was funded by the National Institute on Aging, part of the National Institutes of Health.

Semaglutide is the active ingredient in Ozempic and Wegovy. This study was done in animals. No people were treated, and no human outcome was measured.

Treatment started at 20 months, late in a mouse life

Laboratory mice of the C57BL/6 strain typically live around two years. The researchers waited until the animals were 20 months old before starting treatment. In rough human terms that is closer to starting a drug in someone's sixties than in their thirties. That choice is the point of the experiment. Many aging studies start treatment in young animals, which tells you little about whether something helps a body that is already old.

The mice received 10 nmol/kg of semaglutide by injection under the skin, once a day. That is a daily schedule at a dose scaled to mouse body weight and mouse metabolism. It is not the once weekly regimen people are prescribed, and the figure does not convert into a human dose.

Median lifespan rose from 742 days to 834 days

Untreated female mice had a median lifespan of 742 days. Treated mice reached 834 days. The difference is 92 days, about 12 percent. Median lifespan is the age by which half the group had died, so it describes the middle of the group rather than the longest lived animals. A shift in the median does not by itself tell you whether the oldest animals lived longer.

The team also ran a separate three month course of treatment to measure function rather than survival, and compared semaglutide against calorie restriction, which is the most consistently reproduced life extending intervention in laboratory animals. Treated mice showed better exploratory drive, better spatial memory and better glucose control.

Body weight fell mainly through loss of fat. The share of the body made up of fat went down and the share made up of lean tissue went up. That detail is worth noting because losing muscle alongside fat is a recognized concern with these drugs in people, particularly in older patients.

Only female mice were tested

The study did not include male mice. Sex differences in aging research are common and sometimes large, so the result cannot be assumed to hold in male animals, and certainly not in men. The paper's own title is specific about this.

One strain of laboratory mouse, housed in controlled conditions and fed a controlled diet, is also a narrow test. Results that hold in one mouse strain and disappear in another are a recurring problem in aging research, which is part of why the National Institute on Aging runs replication programs across multiple sites.

Nothing here changes how the drug should be used

The authors write that whether GLP-1 receptor activation changes aging in humans "will require long-term clinical studies designed to evaluate ageing-related outcomes in older populations." The NIH summary of the work said the findings "do not imply that similar results could be achieved immediately in humans."

For anyone currently taking semaglutide, the practical content of this study is nothing. It is not a reason to take a higher dose, to take it for longer, or to take it for a purpose a prescriber did not intend. Questions about dose and duration belong with the clinician who wrote the prescription, working from the approved labeling and the person's own history.