Semaglutide is a synthetic analogue of glucagon-like peptide-1 (GLP-1), a hormone the gut releases after eating. Structural changes to the natural peptide, including a fatty-acid chain that binds it to albumin in the blood, extend its half-life from minutes to roughly a week. That is what makes weekly dosing possible.
It is among the most thoroughly studied compounds described anywhere on this site. Large randomised trials have measured its effects on blood glucose, body weight and cardiovascular outcomes, and it holds regulatory approval in multiple jurisdictions. That places it in a different evidence category from most research peptides, and the profile below reflects that.
The corollary is worth stating plainly: material bought as a research chemical is not the approved medicine. The trials below tested a product manufactured to pharmaceutical standard, with a known quantity of a known substance in each vial. That is the thing being evidenced, and it is not what is being sold on the gray market.
How it works
GLP-1 receptors sit in the pancreas, the stomach, and parts of the brain that regulate appetite. Activating them prompts the pancreas to release insulin when blood glucose is high, suppresses glucagon, and slows the rate at which the stomach empties.
The appetite effect appears to be largely central rather than digestive: receptor activity in the hypothalamus and brainstem reduces hunger and increases the sense of fullness after a smaller meal. The slowed gastric emptying contributes, and is also the source of the nausea commonly reported in trials, particularly while a dose is being increased.
Regulatory status — United States
Approved by the FDA as a prescription medicine for type 2 diabetes and for chronic weight management. Material sold as a research chemical is not the approved product — is not manufactured to the same standard — and is not legal to sell for human use.
Last reviewed 12 Aug 2026. Regulatory positions in this category change frequently; we date this line so you can see how current it is.
What it is studied for
Each entry states the evidence behind it. We do not rank indications by effectiveness — for most compounds here, that would be a claim nobody can support.
Weight management
Clinical trialApproved for chronic weight management alongside diet and activity.
EvidenceLarge randomised placebo-controlled trials in adults with obesity, run over 68 weeks.
Type 2 diabetes
Clinical trialApproved for glycaemic control in type 2 diabetes.
EvidenceMultiple phase 3 trials.
Identity and clearance
Molecule
- Class
- GLP-1 receptor agonist, acylated analogue
- Molecular weight
- 4113.58 Da
- Length
- 31 amino acids
A modified GLP-1 backbone with a C18 fatty diacid chain. That chain binds albumin in the blood. That is what slows clearance enough for weekly dosing.
Pharmacokinetics
Clinical trialA half-life near seven days means roughly five weeks pass before a dose is substantially cleared, and that any dose change takes weeks to show its full effect.
Dose protocols reported in sources
Displayed for reference only. Every row says where it came from, and a trial protocol and a community convention are not the same kind of information. None of this is fed into the calculator, and none of it is a recommendation.
| Goal | Dose | Frequency | Route | Units, 3 mg vial | Source | Start this protocol |
|---|---|---|---|---|---|---|
| Trial escalation, weeks 1–4 | 250 mcg | Once weekly | Subcutaneous | 8.33 u | Clinical trial | Start this |
| Trial escalation, weeks 5–16 | 500 mcg – 1.7 mg | Once weekly, raised in steps every four weeks | Subcutaneous | 16.67–56.67 u | Clinical trial | Start this |
| Trial maintenance dose | 2.4 mg | Once weekly | Subcutaneous | 80 u | Clinical trial | Start this |
Start this copies a row into a protocol of your own, which you can then edit. Where a source gave a dose range or an ambiguous frequency, those fields arrive empty — we will not pick a number on your behalf.
Calculator
Work out what to draw
Pre-filled with a 5 mg vial as a worked example. These are not recommended values — change them to match the vial in front of you.
Draw to 10 units on a 1 mL U-100 syringe. That is 0.1 mL, containing 250 mcg of Semaglutide.
10 units sits exactly on a printed line.
Bioalmanac performs arithmetic on values you enter. It does not recommend doses, schedules or compounds, and nothing here is medical advice. Confirm every calculation against your vial and syringe before drawing, and speak with a licensed healthcare provider.
Open this calculation in the full calculator
Units, concentration, bacteriostatic water — the glossary defines the vocabulary, and a unit is not a fixed volume.
Safety
Reported effects
- NauseaClinical trial
Very common in trials
The most frequently reported effect, worst in the days following a dose increase and usually settling as the dose is held.
- Diarrhoea, constipation, vomitingClinical trial
Common in trials
- Reduced appetite and early fullnessClinical trial
Very common
The intended effect, but it can go far enough to make adequate protein and fluid intake difficult.
- Gallbladder problems, including gallstonesClinical trial
Uncommon but documented
Associated with rapid weight loss generally as well as with the drug itself.
- PancreatitisClinical trial
Rare
Severe, persistent abdominal pain radiating to the back is the presentation to act on.
- Loss of lean mass alongside fatClinical trial
Documented in trials
A substantial share of weight lost can be lean tissue. Resistance training and adequate protein are the usual countermeasures.
When to stop
- Severe, persistent abdominal pain, especially radiating to the back and with vomiting. That is the presentation of pancreatitis. Seek urgent medical care.
- Persistent vomiting or inability to keep fluids down. Dehydration is the most common route to serious trouble on these drugs.
- Signs of gallbladder disease: pain in the upper right abdomen, fever, or yellowing of the skin or eyes.
- A lump or swelling in the neck, hoarseness, or difficulty swallowing.
- Any allergic response: rash, hives, facial swelling, or difficulty breathing. Seek urgent care.
- If you become pregnant or are planning to.
Interactions and situations that need care
- Personal or family history of medullary thyroid carcinoma, or MEN 2Avoid
The approved products carry a boxed warning on this basis, following thyroid C-cell tumours in rodent studies.
- History of pancreatitisUse caution
Pancreatitis is a documented if uncommon adverse event, and prior episodes raise the stakes of another.
- Pregnancy and breastfeedingAvoid
Not recommended in pregnancy. Given the long half-life, trial protocols called for stopping well in advance of a planned conception.
- Insulin or sulfonylurea therapyUse caution
Combining glucose-lowering agents raises hypoglycaemia risk, and doses of the other agent often need adjusting by whoever prescribes them.
- History of eating disordersUse caution
A drug whose primary effect is appetite suppression interacts with restrictive eating patterns in ways that warrant clinical oversight rather than self-management.
- Planned surgery or general anaesthesiaUse caution
Delayed gastric emptying means the stomach may not be empty after standard fasting, which is an aspiration risk under anaesthesia. Tell your anaesthetist.
What to expect
- In the STEP 1 trial, participants on 2.4 mg weekly lost around 15% of body weight on average over 68 weeks, against about 2.4% on placebo, with diet and activity support throughout.
- Effects build slowly. The escalation schedule spans roughly four months before the maintenance dose is reached.
- Averages are not individuals. Trial results include people who lost far more and people who lost very little.
- Weight regain after stopping is well documented in follow-up studies. These were tested as ongoing treatments, not as a course.
Storage and handling
- Freeze-dried powder
- Refrigerated at 2–8 °C and protected from light. Stable for far longer than the reconstituted form.
- After mixing
- Refrigerated at 2–8 °C. Do not freeze. Discard if the solution is cloudy or has visible particles.
- Long-term, frozen
- Unopened lyophilised powder is stable at −20 °C or colder.
With other peptides
- Tirzepatideincompatible
Both act on the GLP-1 receptor. Combining them stacks the same mechanism rather than adding a new one, and compounds the gastrointestinal effects.
- Retatrutideincompatible
Overlapping GLP-1 agonism. These are alternatives to one another, not a stack.
- Liraglutideincompatible
Both are GLP-1 receptor agonists. Taking them together doubles the gastrointestinal effects and the pancreatitis risk while adding nothing. The receptor is already saturated at therapeutic doses of either.
- Cagrilintidesynergistic
The pairing under active development as CagriSema. Amylin and GLP-1 signal satiety through different receptors, so the effects add rather than overlap. The trial evidence is for a single manufactured combination product, not for mixing two separately sourced vials.
- Orforglipronincompatible
Both activate the GLP-1 receptor. Taking them together doubles the gastrointestinal effects and the pancreatitis risk while adding nothing — the receptor is already saturated at therapeutic doses of either.
- Mazdutideincompatible
Both fully activate the GLP-1 receptor. Running them together stacks one mechanism and its side effects rather than adding anything.
- Survodutideincompatible
Overlapping GLP-1 agonism. Running them together stacks one mechanism and its side effects.
- Eloralintidecaution
Amylin and GLP-1 signal satiety through different receptors, which is the basis of the CagriSema combination. No trial has tested this pairing, and stacking two strong appetite suppressants risks intake falling below what is safe.
In use
Stacks with Semaglutide in them
Documented combinations, with full schedules.
Checking your vial
Research chemicals carry no manufacturing standard, so what the vial looks like is often the only quality signal available before you use it. More on assessing quality and COAs.
White cake, clear solution
Correctly lyophilised powder forms a white cake and mixes to a completely clear solution.
Collapsed or melted cake
Indicates heat exposure in transit.
Cloudiness or particles after mixing
Do not use. This is also the standard instruction for the approved product.
Questions
- How long does semaglutide take to leave the body?
- Its half-life is around a week, so roughly five weeks pass before it is substantially cleared. This is why trials escalate the dose slowly and why a missed week does not produce an immediate drop-off.
- Why do trial protocols increase the dose so gradually?
- Gastrointestinal side effects, nausea above all, are strongly dose-related and worst when a dose first increases. Trial protocols raise the dose in steps over months specifically to limit that.
- Does it need to be taken on the same day each week?
- Trial protocols specified a fixed weekly day. With a half-life of about seven days, moving the day by a small amount changes blood levels very little, but a fixed schedule is easier to keep track of and is what was studied.
References
Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1)
New England Journal of Medicine, 2021 · Randomised, double-blind, placebo-controlled phase 3 trial
Adults with overweight or obesity, without diabetes · n = 1961 · 2.4 mg once weekly, after 16 weeks of escalation · 68 weeks
Mean weight change of −14.9% with semaglutide against −2.4% with placebo. Gastrointestinal effects were the most common adverse events and were mostly transient.
10.1056/NEJMoa2032183
Semaglutide compared with
Semaglutide vs liraglutide
Same receptor, same drug class, one generation apart. One is a weekly injection and produced about twice the weight reduction of the other, which is a daily one.
Retatrutide vs semaglutide
One receptor against three, and a finished approval against a trial programme still running. The largest reported effect in the class, set beside the most established one.
Semaglutide vs cagrilintide
Two different satiety pathways, usually discussed as a pair rather than a choice. One is an approved drug on its own; the other is mostly studied alongside it.
Semaglutide vs tirzepatide
Both are once-weekly incretin agonists approved for weight management. The difference is how many receptors each one acts on, and what that does to the dosing scale.
Related compounds
Tirzepatide
A once-weekly dual agonist that activates both the GIP and GLP-1 receptors, approved for type 2 diabetes and for weight management.
Retatrutide
An investigational once-weekly triple agonist acting on the GLP-1, GIP and glucagon receptors. Not approved anywhere.
Liraglutide
The first GLP-1 analogue approved for weight loss. A daily injection, superseded by weekly semaglutide but still the best-documented compound in the class.
Cagrilintide
A long-acting amylin analogue in late-stage trials. It works on a different satiety pathway from the GLP-1 drugs. Which is why it is being developed alongside semaglutide rather than against it.
Next
What to do with Semaglutide
- Keep a record of itTurn a dose and a schedule into a protocol, then log what you actually take. Semaglutide is filled in for you.
- See what it costsPer-milligram prices read from vendor sites and confirmed by a person, so vial sizes compare.
- Check a combinationWhat our profiles record about Semaglutide alongside each other compound — including the pairs where nothing is recorded.
Keep this page honest
If something here is wrong, out of date, or missing a source, tell us and we will fix it and say that we did.
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice. No clinician reviews these pages.
Page last updated 12 Aug 2026