Strong evidence · Grade A
Semaglutide
Semaglutide (Ozempic / Wegovy / Rybelsus)
Score
88 / 100
Half-life
~7 days
Brand
Ozempic · Wegovy
FDA
2017
TL;DR
01
Among the best-evidenced peptides in the library — two large randomized trials (STEP-1, SUSTAIN series) show 14–16% average weight loss at one year.
02
Originally approved for type 2 diabetes (2017) and later for chronic weight management (2021 as Wegovy). Oral version (Rybelsus) exists for diabetes.
03
Side-effect profile is real: nausea, early satiety, and GI discomfort are near-universal in the titration phase. Thyroid C-cell tumor warning in rodents (black box).
04
Not for everyone — personal or family history of medullary thyroid carcinoma or MEN-2 is an absolute contraindication.
Trial weight loss
−14.9%
STEP 1 · 68 wk
CV risk
−26%
SUSTAIN-6 · MACE
Peak nausea
44%
wk 1–8; resolves
Retention
46%
real-world · 12 mo
Regain off-drug
+⅔
1 yr post-stop
Part 01 · How it works
Mechanism.
Semaglutide mimics a gut hormone your body normally makes after you eat. It tells your pancreas to release insulin only when blood sugar is actually high, slows how quickly your stomach empties, and dampens the appetite signals in the brain. The net effect is that you feel full sooner, stay full longer, and your blood sugar is more stable — all without the hypoglycemia that comes with older diabetes drugs.
Think of it as a dimmer switch on hunger — not an off switch. It doesn't make food revolting; it makes portion sizes feel natural.
GLP-1R agonism
Binds the GLP-1 receptor (a class B GPCR) on pancreatic β-cells, activating adenylyl cyclase → cAMP → PKA/EPAC2 signaling → glucose-dependent insulin secretion.
Gastric emptying
Delays gastric emptying via vagal afferents, flattening the postprandial glucose curve. Tolerance to this effect develops over 4–8 weeks of continuous use.
CNS satiety
Crosses the blood-brain barrier at low levels; acts on arcuate nucleus POMC neurons and area postrema to suppress appetite and increase satiety.
Glucagon suppression
Reduces glucagon release from α-cells in a glucose-dependent manner — contributes to fasting glucose control without causing hypoglycemia.
Half-life engineering
The fatty diacid side chain binds albumin reversibly; this is the mechanism behind the ~7-day half-life and once-weekly dosing.
Part 02 · Dosing & administration
How it's taken.
Values below describe how Semaglutide has been administered in published trials and labeling. Provided for educational purposes only — this is not medical advice and not instructions for self-administration. Consult your healthcare provider before making any health decision.
Wk 1–4
0.25 mg
Starter — minimize GI effects
Wk 5–8
0.5 mg
First step up
Wk 9–12
1.0 mg
Second step up
Wk 13–16
1.7 mg
Third step up
TARGET
Wk 17+
2.4 mg
Maintenance (weight management)
·
Step up every 4 weeks minimum — faster titration sharply increases GI side effects.
·
If a dose is missed, take it within 5 days, then resume weekly schedule. If >5 days, skip and dose normally next week.
·
Rotate injection sites (abdomen / thigh / upper arm) to reduce local lipohypertrophy risk.
Need help with reconstitution?
Use the free peptide calculator for dilution, unit conversion, and injection volume.
Part 03 · Safety
Side effects, rare serious events, who shouldn't.
Common
Nausea
Usually peaks in first 8 weeks; largely resolves.
44%
Diarrhea
Often transient; hydration important.
30%
Vomiting
Dose-limiting for some patients.
24%
Constipation
High-fiber diet helps.
24%
Abdominal pain
Should resolve; persistent severe pain warrants pancreatitis workup.
20%
Serious · rare
Pancreatitis
Severe abdominal pain radiating to back — seek urgent care.
<1%
Gallbladder disease
Rapid weight loss risk factor independent of drug.
1.6%
Diabetic retinopathy (in T2D)
Usually transient with glucose correction; monitor.
3%
Severe GI / gastroparesis
Emerging signal — see research log #7.
<1%
Thyroid C-cell tumors
Not observed in humans; black box warning remains.
Rodent signal only
Absolute · do not use
×
Personal or family history of medullary thyroid carcinoma (FDA boxed warning)
×
Multiple endocrine neoplasia syndrome type 2 (MEN2) (FDA boxed warning)
×
Known hypersensitivity to semaglutide or any component
×
History of pancreatitis
×
Pregnancy or breastfeeding (discontinue at least 2 months before planned pregnancy per FDA label)
×
Severe gastrointestinal disease (gastroparesis, inflammatory bowel disease)
×
Diabetic retinopathy (may worsen with rapid glucose improvement)
Relative · discuss first
!
History of pancreatitis — proceed only with GI / endocrine input
!
Severe gastroparesis at baseline
!
Active eating disorder — complex risk/benefit
!
Age > 75 with frailty — dose cautiously, monitor weight trajectory
!
Planned surgery within 1 week — discontinuation often recommended
Interactions
Insulin
Per FDA label: increased risk of hypoglycemia; consider reducing insulin dose when initiating semaglutide
Major
Sulfonylureas (glipizide, glimepiride)
Per FDA label: increased risk of hypoglycemia; consider sulfonylurea dose reduction
Major
Oral medications with narrow therapeutic index (warfarin, levothyroxine)
Semaglutide delays gastric emptying which may affect absorption kinetics of oral medications; monitor drug levels
Moderate
Oral contraceptives
Delayed gastric emptying may reduce absorption; consider non-oral contraceptive methods or take pill 1 hour before semaglutide
Moderate
Labs to monitor
HbA1c
Baseline and every 3 months
Primary efficacy marker for glycemic control
Fasting Glucose & Insulin
Baseline and monthly initially
Monitor glycemic parameters
Lipase & Amylase
Baseline and if symptomatic
Screen for pancreatitis (GLP-1 class warning)
CMP (Comprehensive Metabolic Panel)
Baseline and every 3 months
Liver and kidney function; monitor for gallbladder disease
Lipid Panel
Baseline and every 3-6 months
Track cardiovascular risk markers
Thyroid Panel (TSH, Free T4)
Baseline and every 6-12 months
Boxed warning for thyroid C-cell tumors (rodent data)
CBC with Differential
Baseline and every 6 months
General safety monitoring
Part 04 · Evidence
How strong is the evidence?
88
Grade A
As strong as peptide evidence gets in 2026. The remaining uncertainties are about long-term use — the drug works; what happens at year 5–10 of continuous use is an open empirical question.
Mechanistic plausibility
GLP-1 biology is among the most thoroughly mapped pathways in metabolic medicine.
94
Animal data
Consistent effects across rodent and primate models, replicated independently.
92
Human trial quality
Multiple phase 3 RCTs with n > 1,000 per arm; FDA-audited.
90
Replication
STEP, SUSTAIN, and PIONEER program results broadly align.
88
Safety signal
Known GI side effects; rare but serious pancreatitis and gallbladder signals.
72
Long-term data
Most RCTs run 68–104 weeks; real-world tails shorter than ideal.
58
Part 05 · Research log
Every study we cite.
We list each study with its methodology, funding source, and our quality grade. Flagged studies aren't dismissed — they're tagged so you can weigh them.
01
2021
New England Journal of Medicine Industry funded
STEP 1 — Once-weekly semaglutide in adults with overweight or obesity
Mean −14.9% body weight vs −2.4% placebo at week 68.
RCT, 68 wk, placebo-controlled · n = 1,961 · Funded by Novo Nordisk; primary analysis protocol pre-registered.
PMID 33567185 ↗
High
02
2016
NEJM Industry funded
SUSTAIN-6 — Cardiovascular outcomes with semaglutide in T2D
26% relative reduction in major cardiovascular events (nonfatal stroke driving).
RCT, 104 wk, cardiovascular endpoint · n = 3,297 · Sponsor-analyzed; FDA re-adjudicated endpoints.
PMID 27633186 ↗
High
03
2022
Nature Medicine Industry funded
STEP 5 — Two-year outcomes of semaglutide 2.4 mg
Weight regain substantial after discontinuation; −15.2% on-drug maintained over 2 yr.
RCT, 104 wk extension · n = 304 · Dropout rate 25% — per-protocol analysis may overstate effect.
High
04
2023
JAMA Network Open
Real-world adherence to semaglutide in commercial claims
At 12 months, 46% of starters remain on-therapy; weight outcomes track RCT loosely.
Retrospective cohort · n = 18,842 · Claims data — no body-weight ground truth; adherence inferred from refills.
Moderate
05
2023
Lancet Gastro Hep Industry funded
Semaglutide and hepatic steatosis — MRI-PDFF trial
Significant liver fat reduction vs placebo; ALT improvement secondary endpoint.
RCT, 48 wk · n = 320 · Sponsor-analyzed; imaging core lab independent.
Moderate-High
06
2017
Diabetes Care Industry funded
PIONEER-1 — Oral semaglutide monotherapy in T2D
HbA1c reduction 0.7–1.4% dose-dependent; GI AEs as injectable.
RCT, 26 wk · n = 703 · Oral formulation uses SNAC absorption enhancer — bioavailability ~1%, so high dose needed.
High
07
2024
JAMA
Gastroparesis risk with GLP-1 agonists — disproportionality analysis
Elevated reporting ratio for severe gastroparesis vs bupropion/naltrexone control.
Pharmacovigilance database · n = 16,000 · FAERS signal detection — reporting bias possible; causality not established.
Moderate
08
2019
Diabetologia Industry funded
Cancer risk signal — SUSTAIN and PIONEER pooled
No increased malignancy signal overall; pancreatic cancer too rare to exclude.
Pooled analysis, 9 RCTs · n = 12,000 · Pooled sponsor trials; rare-event sensitivity limited.
Moderate
09
2025
Preliminary — press release Preliminary
Semaglutide in early Alzheimer's (evoke / evoke+)
Primary endpoint missed; secondary analyses ongoing.
RCT, 104 wk · n = 3,800 · Full manuscript pending — interpret cautiously.
Moderate
10
2024
Regulatory summary
Suicidality signal — EMA and FDA review
No causal association found after structured review; residual uncertainty acknowledged.
Post-marketing review · Regulator reviews — conservative by design; meta-analyses pending.
N/A
Part 06 · Cost & access
Where it's available, at what price.
United States
FDA-approved
Rx via PCP / endocrinology. Insurance coverage variable for weight indication.
$900–1,300/mo cash; ~$0–200/mo with coverage
United Kingdom
NHS approved (restricted)
Wegovy available via NHS specialist weight-management services; private Rx widely available.
£150–250/mo private
European Union
EMA approved
Prescription; coverage varies by country.
€200–400/mo
Canada
Health Canada approved
Rx only. Wegovy launched 2024; provincial coverage variable.
CAD 400–500/mo
Australia
TGA approved
Rx; weight indication not PBS-subsidized.
AUD 400–550/mo
Research-grade / compounded
Gray-market
Not FDA-approved compounded preparations exist; quality varies widely; we recommend only pharmacy-compounded products with third-party testing.
$150–350/mo
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Part 07 · Your appointment
Questions to bring.
01
Which semaglutide formulation and indication best fits my clinical situation — diabetes management, weight loss, or cardiovascular risk reduction?
02
What is the plan if I stop semaglutide — how do we maintain benefits or transition to another approach?
03
Am I at risk for the rare but serious side effects like pancreatitis or diabetic retinopathy worsening?
04
Does my family history of thyroid cancer affect whether I should take semaglutide?