Tirzepatide Research: Results and Limits
How tirzepatide changes hunger and blood sugar
Its makers designed tirzepatide to act like two hormones released from the gut. GLP-1 helps with hunger, while GIP helps send insulin into the blood after food. They hoped to smooth blood sugar swings and lessen hunger. That’s why a study result tells you more than a dish test.
GLP-1 can slow food leaving the stomach. GIP prompts the pancreas to send insulin into your blood as sugar rises. In dish tests, tirzepatide’s GLP-1 effect was about five times weaker than the body’s own GLP-1, but lasted longer [1]. The test didn’t show who would improve.
Here’s what the studies point to: four main changes. Food remained longer after meals, helping people feel full. The body released more insulin after meals and less of the blood-sugar-raising hormone glucagon. Lab dish cells also released stored fat during fasting when GIP was active [21].
SURPASS-1 was short, had 10-15 mg study groups, and found that only 13-21% of the gain in how well insulin worked came from weight loss [13], which means weight loss didn’t cause most of that gain. A test of insulin-making cells improved 77-92%. Proinsulin, the raw material those cells turn into insulin, fell 49-55%, showing less strain.
At your visit, ask which change the clinician hopes to see. I’d also ask when your blood test or weight will be checked. No dish finding can promise how you’ll feel [1][21].
What tirzepatide changed in diabetes studies
Five studies called SURPASS-1 through SURPASS-5 put adults with type 2 diabetes into groups by chance. Together, they included 6,263 people. With 5, 10, or 15 mg, the test for recent average blood sugar went down 1.9% to 2.6% during 40-52 weeks [5].
More than 90% got that blood sugar test below 7.0%. At some point, at least 80% got 6.5% or less. Those weren’t personal pass-or-fail marks for you. Your clinician can explain what number fits your health.
SURPASS-1 was a 40-week study with 478 people. That same test dropped 1.87%, 1.89%, and 2.07% in the 5, 10, and 15 mg groups. It rose 0.04% with placebo, a comparison shot without tirzepatide. In the drug groups, 81-86% reached 6.5% or less [2].
SURPASS-3 was a 52-week study with 1,437 people. With 15 mg, that test dropped 2.37%, compared with 1.34% on daily insulin. Body weight fell 7.5-12.9 kilograms with tirzepatide and rose 2.3 kilograms with insulin [4]. A kilogram is a little more than two pounds.
In that study, 82-93% got the average-sugar blood test below 7.0%. The share was 61% with insulin. SURPASS-3 and SURPASS-4 also compared one weekly shot with daily insulin. More than 90% stayed with the plan they were given [4][5].
SURMOUNT-1 tracked body weight for 72 weeks. Average loss was 22.5% in the 15 mg group. Under one way of counting people who stopped, the 5 mg group lost 16.0%; the 10 mg group lost 19.5% [6]. At the time, there wasn’t a larger average in an approved-drug study.
What tirzepatide changed in body weight and muscle
SURMOUNT-1 followed 2,539 adults with obesity for 72 weeks. None had type 2 diabetes. Under the other way of counting people who stopped, the 5 mg result was 15%; average loss was 19.5% with 10 mg and 22.5% with 15 mg. The placebo group lost 2.4% [6].
Only 160 people in SURMOUNT-1 had body scans. In the three drug groups, 89.4%, 96.2%, and 96.3% lost at least 5% of starting weight. In this small group, body fat fell 33.9%, compared with 8.2% on placebo. Muscle and other tissue fell 10.9%, compared with 2.6% [7].
Fat made up 75% of all weight lost. Muscle and other tissue made up 25%. This small scan study can’t settle how your muscle will change. Ask whether strength work and enough protein fit your care.
SURMOUNT-4 had 670 people after a 36-week first part. At week 36, SURMOUNT-4 moved some people to placebo. During the next 52 weeks, they regained about half their lost weight, or 14.0% from the week 36 low. The SURMOUNT-4 group staying on tirzepatide lost 5.5% more, reaching 25.3% from the start [8].
There isn’t much long follow-up yet. SURMOUNT-2 and two SURMOUNT-4 reports reached 88 weeks. At the 176-week mark in the heart study, half were watched longer and half for less time. Your clinician may still watch thyroid and pancreas health [8][11].
What tirzepatide did beside semaglutide
Ozempic contains semaglutide, the medicine used for comparison here. Two studies directly compared tirzepatide vs semaglutide. SURPASS-2 included adults with type 2 diabetes, while SURMOUNT-5 studied adults with obesity who didn’t have type 2 diabetes. They’re different groups, so the studies answer different questions.
SURPASS-2 was a 40-week study of 1,879 people with type 2 diabetes. The recent-average-sugar test dropped 2.01%, 2.24%, and 2.30% with tirzepatide 5, 10, and 15 mg. It dropped 1.86% with semaglutide 1 mg. Body weight fell 7.6, 9.3, and 11.2 kilograms, compared with 5.7 kilograms; this gap was larger than chance could explain [3].
SURMOUNT-5 came out in 2025. It placed 751 people into groups by chance for 72 weeks. Average body-weight loss was 20.2% with tirzepatide and 13.7% with semaglutide 2.4 mg. Loss of 30% or more occurred in 19.7% and 6.9% [10].
Waist size fell 18.4 centimeters with tirzepatide and 13.0 centimeters with semaglutide. That’s less than half an inch for each centimeter. This was the only published direct study of these obesity drugs at the time. It can’t decide which medicine fits you; health, cost, and follow-up time also count.
Researchers haven’t proved why the weight results differed. Tirzepatide uses both gut hormones; semaglutide uses just one. Lab dish cells released stored fat when GIP was active [21]. That work gives a possible reason, not an answer about people.
What tirzepatide changed in blood pressure and heart risk
Across SURPASS-1 through SURPASS-5, the upper blood-pressure reading fell 2.8 to 12.6 millimeters of mercury. In SURPASS-4, 43-67% of that drop went along with weight loss. Other body changes accounted for 33-57% [12]. The study couldn’t name one cause for each person.
The largest drops came when the starting top number was above 140 millimeters of mercury. People who began with a normal reading didn’t clearly have more dangerously low pressure [12]. That’s useful, but it can’t forecast your reading. Ask how often your clinic will check it.
The heart study followed 13,299 adults with type 2 diabetes and high heart risk. At the 176-week mark, half had been watched longer and half for less time. The combined count of heart attack, stroke, and heart-related death wasn’t higher with tirzepatide than with another diabetes drug. Researchers were 95% sure the true result lay between a small benefit and tiny possible harm [11].
A later check counted fewer deaths overall among those taking tirzepatide. The researchers’ 95% estimate also leaned toward fewer deaths. This wasn’t the study’s main question, so that answer is less sure. Ask what the heart finding means for you.
Across SURPASS and SURMOUNT, the top number often fell 4-11 millimeters of mercury [12]. Larger drops came with higher starting pressure and more weight loss. Your clinician can compare those findings with your home readings. Don’t change a blood pressure pill from one study result.
What tirzepatide changed in sleep apnea
Two short studies from 2024 enrolled adults who had both obesity and worse sleep apnea. One studied people who didn’t use a breathing machine. The other kept people on their machines. They’re both studies that placed people into groups by chance.
Without a machine, breathing stops fell 25.3 times each hour with tirzepatide. They fell 5.3 times with placebo, the comparison treatment, for a gap of 20.0 stops each hour. Chance couldn’t readily explain a gap that large. Low-oxygen time, a blood sign of swelling, and the upper pressure reading also fell [9].
FDA approval came in December 2024 for adults with worse sleep apnea who also had obesity [9][16]. Tirzepatide was the first drug approved for that use. Approval doesn’t mean you can stop a breathing machine. You’d make that choice with your sleep clinician.
The tirzepatide sleep apnea research points mainly to weight loss. Less fat around the airway may help air move. GLP-1 might also affect throat muscles, but that idea hasn’t been proved in people. There isn’t enough evidence yet.