Liraglutide vs Semaglutide: What Research Shows and What to Track

Liraglutide and semaglutide are both GLP-1 medicines, and they often come up in the same conversation. One is an older daily injection. The other is a newer weekly one. People who use a GLP-1 tracker often ask how the two compare in research, and what changes in their records if a provider ever moves them from one to the other.

This post walks through what the main trials actually reported, in plain language. It is not a guide to choosing a medicine. That decision belongs to you and a licensed healthcare provider who knows your history.

What liraglutide and semaglutide have in common

Both are GLP-1 receptor agonists. In simple terms, they act like a natural gut hormone called GLP-1, which is involved in blood sugar control and appetite signals.

According to MedlinePlus, the NIH's drug information service, liraglutide injection is used to help control blood sugar in certain people with type 2 diabetes, to lower the risk of heart attack and stroke in some adults with type 2 diabetes and heart disease, and to assist with weight loss in certain people with obesity or overweight and weight related health problems. Different brand names cover different uses, which is one reason the exact product on your prescription matters for your records.

The biggest practical difference is the rhythm. MedlinePlus describes liraglutide as an injection used once a day. Semaglutide for weight management is a once weekly injection. That one detail shapes almost everything about how you keep track.

What the research says about liraglutide on its own

The key weight management study for liraglutide is the SCALE Obesity and Prediabetes trial, published in the New England Journal of Medicine in 2015. You can read the SCALE trial abstract on PubMed.

Here is what it reported:

• It was a 56 week, double blind trial with 3,731 adults who did not have type 2 diabetes.
• Everyone, on liraglutide or placebo, also got counseling on lifestyle changes.
• People in the liraglutide group lost an average of 8.4 kg, compared with 2.8 kg in the placebo group.
• About 63 percent of the liraglutide group lost at least 5 percent of their starting weight, compared with about 27 percent on placebo.
• The most common side effects were mild or moderate nausea and diarrhea.

These are averages across thousands of people. Individual results in the study varied widely, and your own experience is something only you and your provider can assess.

What happened when the two were compared head to head

For years there was no direct comparison. Then came STEP 8, a randomized trial published in JAMA in 2022. Here is the STEP 8 trial abstract on PubMed.

How STEP 8 was set up

• 338 adults with overweight or obesity, without diabetes, at 19 sites in the United States.
• Participants got weekly semaglutide, daily liraglutide, or a matching placebo, plus diet and physical activity counseling.
• The trial ran for 68 weeks.
• The comparison between the two medicines was open label, meaning participants knew which one they were on.

What STEP 8 reported

• Average weight change was about 15.8 percent with semaglutide and 6.4 percent with liraglutide. The pooled placebo group changed by about 1.9 percent.
• About 71 percent of the semaglutide group reached 10 percent weight loss or more, compared with about 26 percent of the liraglutide group.
• Stomach and gut side effects were common and similar in both groups, reported by about 84 percent on semaglutide and about 83 percent on liraglutide.
• More people stopped treatment for any reason in the liraglutide group (about 28 percent) than the semaglutide group (about 14 percent).

How to read these numbers

STEP 8 was funded by the company that makes both medicines, which the paper discloses. It was also fairly small and open label. The results are meaningful, but they describe group averages in a specific study population. They do not predict what any one person will experience, and they are not a reason to change anything on your own. If you have questions about which medicine fits you, bring them to your provider.

Why daily versus weekly changes how you track

Whatever your provider prescribes, the injection rhythm changes what a good record looks like.

Tracking a daily injection

With a daily medicine, there are seven injections a week instead of one. That means:

• More chances for a missed or late dose, so a simple on time record is very useful.
• More injection sites in a short span, so rotation matters more. Writing down where each injection went helps you avoid reusing the same spot.
• Pens run out faster, so knowing how many days are left in the current pen saves a last minute pharmacy run.

Tracking a weekly injection

With a weekly medicine, the risk flips. Missing a dose is less likely, but forgetting whether you already took it this week is common. A clear log with the day and time of each injection settles that question fast.

Tracking a switch between the two

If a provider moves you from one GLP-1 to another, your records become extra valuable. Useful details to write down include:

• The date of your last dose of the old medicine and the first dose of the new one.
• The exact dose your provider gave you for each step, written the way your provider wrote it.
• Any side effects in the first few weeks, with a simple rating of mild, moderate or severe.
• Your weight on a consistent day and time, so the trend is easy to read.

Never work out a new dose or a switching schedule yourself. Those details come from your provider.

What to bring to your appointments

A short summary makes it much easier to talk through how things are going. Before a visit, gather:

1. Your on time rate for the last few weeks, and any missed doses.
2. The current step on your provider's plan and when it started.
3. A weight trend, not just a single number.
4. Side effects, when they happened, and how strong they felt.
5. Questions you want answered, written down so you do not forget them in the room.

This is record keeping, not self assessment. Your provider interprets the trend. Your job is just to make it visible.

Keeping your GLP-1 records in Peppy

Peppy is a peptide and GLP-1 tracker for iPhone that keeps this kind of record in one place. You can log each dose, set dose reminders that fit a daily or weekly rhythm, and see your on time percentage in your dose history. Weight and side effect check-ins sit next to your doses through weight tracking, which makes the appointment summary above easy to pull together. If you are on semaglutide, the semaglutide tracker page shows how that fits together.

There is no account to create, and your data stays on your iPhone and your own iCloud backup.

If you also track a peptide that comes as a powder in a vial, the free peptide calculator shows how the vial strength, the water added and the dose your provider gave you translate into units on a syringe. It does the math only. The dose itself always comes from your provider.

The short version

• Liraglutide is a daily GLP-1 injection, and semaglutide for weight management is weekly.
• In the SCALE trial, liraglutide was linked to more weight loss than placebo, with nausea and diarrhea as the most common side effects.
• In STEP 8, average weight loss was larger with semaglutide than liraglutide, with similar rates of stomach side effects.
• Daily and weekly schedules call for slightly different tracking habits, and a switch between them is worth documenting carefully.
• Every decision about which medicine to use, and at what dose, belongs to a licensed healthcare provider.