Semaglutide vs Tirzepatide: A Nurse Practitioner's Honest Comparison

"Okay, so which one should I be on?"

I get asked some version of this question almost every week. A client sits down across from me, pulls out a notes app full of TikTok screenshots, and asks if I should put her on semaglutide or tirzepatide. Ozempic or Mounjaro. Wegovy or Zepbound.

Real talk: I get it. I've been the woman holding the printout, too. When I was losing my own hundred pounds, I read everything I could get my hands on, and I still ended up sitting across from a provider asking, "okay, but for me, which one?" That question deserves a real answer, not a TikTok caption.

Until last year, we honestly didn't have a clean apples-to-apples answer. We had two excellent medications, each with great data on their own, but very few studies that put them in the same room and let them compete. That changed in May 2025 when the SURMOUNT-5 trial was published in the New England Journal of Medicine. So let me walk you through what we know now, what we still don't, and how I actually make the call in clinic.

What These Two Medications Actually Are

Semaglutide and tirzepatide both belong to a class of drugs originally developed for type 2 diabetes that turned out to be remarkable for weight loss. They work by mimicking gut hormones your body already makes after a meal. But they're not the same molecule, and the difference matters.

Semaglutide (the active ingredient in Ozempic, Wegovy, and most compounded GLPs) is a single agonist. It activates the GLP-1 receptor, which slows how quickly food leaves your stomach, helps your pancreas release insulin when blood sugar rises, and quiets the brain signals that drive food cravings.

Tirzepatide (the active ingredient in Mounjaro and Zepbound) is a dual agonist. It activates both the GLP-1 receptor and a second one called GIP. The way I explain GIP to clients: it adds a layer of insulin sensitivity and fat-metabolism signaling on top of everything GLP-1 already does. It's a more comprehensive nudge to the system.

Same family. Different toolset.

What the Head-to-Head Data Actually Shows

SURMOUNT-5 randomized 751 adults with obesity (and without type 2 diabetes) to either tirzepatide at the highest tolerated dose (10 or 15 mg) or semaglutide at the highest tolerated dose (1.7 or 2.4 mg). Both were given once weekly as a subcutaneous injection. The trial ran for 72 weeks.

Here's what they found:

• Average weight loss: 20.2% with tirzepatide vs. 13.7% with semaglutide. That's roughly 47% more weight loss on average with tirzepatide.
• Big losers: 31.6% of people on tirzepatide lost at least a quarter of their body weight, compared to 16.1% on semaglutide.
• Waist circumference: Tirzepatide reduced waist size by about 18.4 cm; semaglutide by about 13.0 cm. That maps roughly to where visceral fat lives, which is the most metabolically dangerous fat.

If you only read the headline, tirzepatide "won." And on average, in this study, it did. But here's the part the headlines skip: 13.7% body weight loss with semaglutide is still a phenomenal result. That number used to be the ceiling we hoped any weight-loss drug would ever reach. The real question isn't "which one is better." It's "which one is right for you?"

Side Effects: Different, Not Better or Worse

Both medications cause GI side effects, especially in the first few weeks as you titrate up. Both have a boxed warning about a rare thyroid tumor (medullary thyroid carcinoma) and shouldn't be used by anyone with a personal or family history of it. That's the baseline.

What's interesting is the flavor of GI side effects:

• Semaglutide more commonly causes nausea and constipation.
• Tirzepatide more commonly causes diarrhea and looser stools; nausea is less common.

And in SURMOUNT-5, the rate of patients quitting the medication because of GI side effects was about twice as high on semaglutide (5.6%) as on tirzepatide (2.7%). The medication you'll actually stay on is the one that matches your gut.

It's not about which one is "stronger." It's about which one is livable. If you've tried a GLP before and it crushed your appetite for a month but then your body adapted, that history matters. If you have IBS that leans constipation-dominant, the semaglutide profile may be the worse fit. If you've had unpredictable diarrhea or recent gallbladder issues, tirzepatide may aggravate them. None of this is "good or bad." It's pattern matching.

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What the Comparison Doesn't Capture

SURMOUNT-5 told us about weight, waist, and short-term tolerability. It can't tell you about everything that actually matters in real life. A few things I think about that the trial doesn't measure:

• Hormonal context. If you're in perimenopause or post-menopause, the picture changes. A separate Mayo Clinic study published in 2025 in The Lancet found that women on hormone therapy lost 35% more weight on tirzepatide than women not on hormone therapy. We dug into that one in detail in an earlier post.
• Skin and body composition. Faster weight loss can mean more facial volume change (the so-called "Ozempic face") and a higher chance of temporary shedding. If your face has historically been the first place to show your weight loss, pacing matters. I've lived this. It's worth thinking about before you start, not after.
• Cost and access. Branded Zepbound and Wegovy carry their own price tags. Compounded versions exist, and they're not identical to the FDA-approved branded products. That's not a knock on compounded; it's just a real conversation we need to have honestly with anyone choosing a long-term path.
• What you'll do after. No one stays on these medications forever in the same way. We've written about the exit ramp separately, but the medication that gets you the most weight loss isn't useful if you don't have a plan for the day you taper.

How We Actually Decide at GlowCo

When a new client comes in asking about GLPs, here's the short version of what runs through my head:

• Starting weight and target. Larger weight loss goals lean me toward tirzepatide first. Smaller, fine-tuning goals can be served by either.
• GI history. See above. Match the side-effect profile to your gut, not against it.
• Prior GLP exposure. If you've already plateaued on semaglutide for six months at the max dose, a switch to tirzepatide is reasonable. If you're brand new, we usually start lower and slower than you'd expect.
• Hormonal status. Anyone in perimenopause or beyond, we're testing hormones. That conversation often expands into our BHRT program.
• Other peptides on the table. Sometimes the better answer isn't a different GLP, it's adding a peptide stack that targets sleep, recovery, or growth hormone signaling alongside a lower GLP dose. That's a real option for the right person.

What you'll never hear me say in clinic: "Tirzepatide is better. Period."

What you might hear: "Based on your history, your hormones, your goals, and your tolerance for side effects, I'd start here, and we'll re-evaluate in eight weeks."

Common Questions, Honest Answers

What's the actual difference between semaglutide and tirzepatide?

Semaglutide activates one gut-hormone receptor (GLP-1). Tirzepatide activates two (GLP-1 and GIP). The dual mechanism is why tirzepatide tends to produce more weight loss on average, though both are highly effective.

Which one is better for weight loss?

In the SURMOUNT-5 head-to-head trial, tirzepatide produced about 47% more relative weight loss than semaglutide over 72 weeks (20.2% vs 13.7%). On average, tirzepatide wins on the scale. But "better for weight loss" depends on what you can tolerate and stay on consistently.

Are the side effects worse with one vs. the other?

The categories are similar (mostly GI), but the pattern differs: semaglutide leans nausea and constipation, tirzepatide leans loose stools and diarrhea. In trials, fewer people quit tirzepatide due to GI side effects (2.7% vs 5.6%).

How long until I see weight loss?

Most patients notice appetite suppression in the first two weeks. Visible weight loss typically starts in weeks four to six. The 72-week trial endpoint is around 18 months, but most people see significant change in the first six months.

Can I switch from semaglutide to tirzepatide?

Yes, and we do this regularly when someone has plateaued or developed intolerable side effects. We don't recommend doing it on your own. It involves dose conversion, a washout window in some cases, and re-titration.

Are compounded versions the same as the branded ones?

No. Compounded semaglutide and tirzepatide are prepared by licensed compounding pharmacies and aren't FDA-approved as finished products in the same way Wegovy or Zepbound are. They can be a reasonable option for the right patient when accessed through accredited pharmacies, but you should know what you're getting and choose the source carefully.

The Bottom Line

Tirzepatide produces more weight loss on average than semaglutide. That's settled science as of 2025. What's not settled is which one is right for the person sitting across from me, because that depends on side-effect tolerance, hormonal context, prior treatment history, cost, and what life is going to look like after.

The medication only ever does part of the job. The plan around the medication is the rest of it. You deserve a plan, not a script.

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This article is for educational purposes and is not medical advice. GLP-1 medications carry important risks, including a boxed warning for the risk of thyroid C-cell tumors. They are not appropriate for everyone. Always consult a qualified healthcare provider before starting, stopping, or switching any medication.

Sources

Aronne LJ, Horn DB, le Roux CW, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine 2025;393:26-36 (SURMOUNT-5 trial).

American College of Cardiology. SURMOUNT-5: Greater Loss of Weight, Waist Circumference With Tirzepatide Than Semaglutide.

Obesity Medicine Association. Tirzepatide vs Semaglutide: A Comprehensive Comparison for Providers.

Cleveland Clinic Consult QD. Tirzepatide Linked to Better Heart Outcomes Than Semaglutide.

Castaneda, Regina et al. "The role of menopause hormone therapy in modulating tirzepatide-associated weight loss in postmenopausal women with overweight or obesity." The Lancet Obstetrics, Gynaecology, & Women's Health, 2025. Read the study