What the drug changes
How Does Semaglutide Work? It copies a gut hormone.
The drug steadies blood sugar, delays food leaving the stomach, and lowers hunger. Some details come from animal work.
What Semaglutide does in plain words
How does semaglutide work? It copies GLP-1, a hormone made by the gut after meals. The body removes that natural hormone in about two minutes, while the medicine keeps the copied effect active for about a week.
The copied effect sends insulin from the pancreas as blood sugar climbs. It also quiets a hormone that tells the liver to send out sugar. The stomach empties at a slower rate, which may help fullness last.
Studies in people show that users often lost weight. The close work on why hunger changed came mostly from mice and rats; in those animals, medicine reached the brain areas that guide eating. This animal work suggests a cause but doesn't prove the same brain action in people.
What makes the drug last longer
Natural GLP-1 is a hormone the gut sends out after food. A body enzyme called DPP-4 clears GLP-1 in about two minutes. Scientists changed the protein part they call 8, one item in its chain, so DPP-4 can't clear semaglutide as fast. The copied GLP-1 effect can then last far longer.
The medicine also rides on a protein carried in blood, which slows removal by the kidneys. About half can remain after a week [17].
What changes in the pancreas and stomach
The pancreas makes insulin, the hormone that moves sugar from blood into the body. Doctors call the copied gut hormone GLP-1. Semaglutide tells the pancreas to send insulin only while blood sugar is rising. This timing makes low blood sugar less likely with semaglutide alone than with some older diabetes drugs.
The GLP-1 effect also quiets a hormone that makes the liver send out sugar. The stomach then empties more slowly, helping fullness last, though that delay can also cause nausea. A 2024 safety review names these as the main blood-sugar effects [5].
What changed in the brains of mice and rats
The close brain findings come from mice and rats, not people. Semaglutide entered brain parts that handle hunger and fullness [4], and the animals then ate less and picked other foods.
Their use of energy stayed level [4]. That points to eating less as the main cause of weight loss, though animal work can't show each step inside a person.
Human studies measured the weight loss itself. In STEP 1, people lost 14.9% of their starting weight on average [1]. The animal work may explain that result, but it can't replace it.
Why one shot can work for a week
Semaglutide rides on a blood protein, allowing one weekly shot to last [17]. The medicine helps the pancreas send insulin when sugar rises [5]. In animals, it also entered brain parts that guide hunger [4]. Those actions help explain steadier sugar and smaller meals.
A slower stomach can bring both help and harm: fullness may last, yet nausea and bowel trouble may follow. The effects page puts personal stories beside the study warnings.
Studies checked metformin for diabetes, warfarin to thin blood, atorvastatin for cholesterol, and digoxin for the heart. Semaglutide didn't change their blood levels enough to matter [12]. That isn't a full medicine check, so your prescriber still needs every medicine you take.