Notes from GLP-1 studies in people
Semaglutide: what a GLP-1 drug changed in twenty years
Large stage 3 studies followed thousands of people. Each result below names the study and the people who took part.
A generative reading of the semaglutide evidence base — GLP-1 receptor pharmacology, the STEP and SELECT trials, and what the literature actually measured.
What Semaglutide changed for weight and heart risk
What has semaglutide changed in people? The drug acts like GLP-1, a hormone made after meals. It is a 31-amino-acid chain, meaning each link is a protein part. The body's GLP-1 fades in ~2 minutes. Semaglutide stays in blood about 168 hours. That's why studies gave one shot each week.
Six large sets of studies were done. Their names are SUSTAIN, PIONEER, STEP, SELECT, ESSENCE, and OASIS. Stage 3 means a large test done late in drug research. Those tests covered weight, liver disease, and alcohol use. They also included teens and people with type 2 diabetes.
In STEP 1, people got a 2.4 mg weekly shot. After 68 weeks, they had lost 14.9% on average. People given a placebo, a shot with no drug, lost 2.4%. Also, 86.4% lost at least 5% of their weight [1].
SELECT followed 17,604 adults with obesity and heart disease. The study lasted an average 39.8 months. Heart death, heart attack, or stroke fell by 20%. Researchers reported 95% confidence in the range around that finding [2].
The FDA cleared three uses for semaglutide. Type 2 diabetes came first, in 2017 and 2019. Weight care with a 2.4 mg shot followed in 2021. Liver disease was added in 2025. Use for those age ≥12 began in 2022.
This isn't a sales or care site. You can use these findings when you talk with your doctor.
What lets Semaglutide last all week
Semaglutide is a peptide, which is a 31-amino-acid chain of protein parts. It acts like the human hormone called GLP-1. The GLP-1 copy matches about 94% of that hormone. Scientists changed three parts so it would last longer.
Those changes sit at parts 8, 34, and 26 of the chain. One keeps the body from breaking the GLP-1 copy down too soon. One prevents the drug from acting like a different gut hormone. The third adds a fat piece. The fat helps the drug hold albumin, a protein in blood.
The GLP-1 drug's hold on albumin slows loss through the kidneys. It also guards semaglutide from fast breakdown. The drug still remains after 4 hours and after 4 days. The result is a ~168-hour half-life [13]. Half-life is the time needed for half the drug to leave.
For you, semaglutide may come as a pill or shot. It acts in the pancreas, gut, and brain. The page on how semaglutide acts like GLP-1 explains how the GLP-1 action reaches each place.
What the FDA has cleared Semaglutide to treat
Which health problems can doctors treat with semaglutide? The FDA added uses over several years.
December 2017 came first. The FDA cleared weekly shots of 0.5 mg and 1.0 mg for type 2 diabetes. September 2019 brought pills of 7 mg and 14 mg for people with type 2 diabetes. The pill includes a helper that lets more drug pass through the stomach wall. It was the first GLP-1 drug sold as a pill.
June 2021 brought a 2.4 mg shot for adult weight care. Use for teens age ≥12 followed in 2022. In 2025, STEP UP tested 7.2 mg and found more weight loss [17]. That amount was still under study.
August 2025 added a use for liver disease. The 2.4 mg shot was cleared for some adults. Their disease, called MASH, scars and harms the liver. In ESSENCE, a large stage 3 GLP-1 study, the disease cleared in 62.9%. It cleared in 34.3% with a placebo [8].
As of 2024, the sports group WADA didn't ban semaglutide. Take these dates to your doctor if a use isn't clear.
What Semaglutide being a peptide means for you
A peptide is a short chain of protein parts. Semaglutide has 31 of those parts. Its size and shape affect how the drug is stored and taken. The drug acts at the same places as the GLP-1 hormone.
The gut doesn't take in this type of drug well. The pill adds a helper so some drug can cross the stomach wall. Semaglutide doesn't move through the whole brain with ease. It reaches certain brain areas that help set hunger.
The drug is larger than many medicines given by shot. It is smaller than many drugs made from antibodies. Factories build the chain and add a fat piece. Filled shot pens hold a cold liquid ready for use.
The body breaks semaglutide into small protein pieces. Common liver steps that clear many pills don't clear this drug [15]. That helps explain why few pills change its blood level.
The semaglutide mechanism of action page follows the drug through the pancreas, stomach, and brain.
What Semaglutide changed in five areas
What have semaglutide studies measured? Five areas stand out. Work on liver disease and alcohol use grew in 2024–2025.
Type 2 diabetes: SUSTAIN-1 through SUSTAIN-10 tracked blood sugar and heart harm in people with type 2 diabetes. SUSTAIN-6 followed 3,297 people at high heart risk. Major heart harm fell 26%. Researchers reported 95% confidence in the range around that result [3].
Weight loss: STEP 1 through STEP 8 included teens and a larger-dose test. Average loss across the studies ran 14–19%. The semaglutide for weight loss page lists each result.
Heart harm: SELECT followed 17,604 adults with obesity but no diabetes. Heart death, heart attack, or stroke fell 20% [2]. The GLP-1 drug's gain wasn't tied only to lower blood sugar.
Liver disease: ESSENCE followed 1,197 people in 2025. Liver disease cleared in 62.9% on semaglutide. It cleared in 34.3% on a placebo [8]. This stage 3 study found less liver swelling and scarring.
Alcohol use: A stage 2 study in 2025 followed 48 people. They had fewer heavy drinking days and less craving [9]. Earlier work found brain changes in animals [10]. Animal findings can't prove the same result in people.