Peptide Profile
Semaglutide
The revolutionary once-weekly GLP-1 medication that helps your body feel full faster and longer, leading to significant weight loss while also protecting your heart—FDA approved and backed by some of the largest clinical trials in obesity medicine history.
Dose Range
0.25-2.4mg
Frequency
Once weekly
Route
Subcutaneous injection
Cycle Length
Ongoing/indefinite
Onset
Moderate (1-2 weeks)
Evidence
Strong
Compound Profile
Scientific & Efficacy Data
C187H291N45O59
Molecular Formula
4113.58 g/mol
Molecular Weight
Approximately 7 days (168 hours)
Half-Life
89% (subcutaneous); 0.4-1% (oral, with absorption enhancer)
Bioavailability
910463-68-2
CAS #
56843331
PubChem ID ↗
Developed By · 2012
Lotte Bjerre Knudsen and team
Novo Nordisk
Primary Benefits
Produces 15%+ average body weight loss in clinical trials—among the most effective non-surgical weight loss interventions ever studied
Dramatically reduces hunger and food cravings by mimicking natural satiety hormones, making portion control feel effortless rather than forced
Proven 20% reduction in cardiovascular events (heart attacks, strokes, CV death) in the SELECT trial—a first for weight loss medications
Amino Acid Sequence
His-Aib-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Val-Ser-Ser-Tyr-Leu-Glu-Gly-Gln-Ala-Ala-Lys(C18 fatty diacid-γGlu-OEG-OEG)-Glu-Phe-Ile-Ala-Trp-Leu-Val-Arg-Gly-Arg-GlyDosing
How much
do I take?
Starting Dose
0.25 mg
This starting dose is designed to let your body adjust to the medication and minimize nausea. You probably won't see much weight loss yet—that's normal. This phase is all about getting your GI system used to the medication.
Standard Dose
0.5-1.0 mg
After 4 weeks at 0.25mg, increase to 0.5mg. After another 4 weeks, move to 1.0mg. This gradual approach significantly reduces nausea and vomiting. Most people start seeing meaningful weight loss at the 0.5-1.0mg doses.
Advanced Dose
1.7-2.4 mg
The 2.4mg dose (Wegovy) is the FDA-approved dose for chronic weight management. Continue increasing by 0.5mg increments every 4 weeks until reaching 2.4mg. This is where the most significant weight loss occurs—averaging 15% or more of body weight in trials.
Timing
Best time to take
Choose any day of the week that works for your schedule and stick with it. Many people prefer Sunday or Monday to make it easy to remember. Take it at roughly the same time each week, though the exact hour doesn't matter much due to the long half-life.
With food?
Semaglutide injections can be taken with or without food—it doesn't affect absorption. However, because the medication slows stomach emptying, eating smaller meals will help reduce nausea. The oral version (Rybelsus) MUST be taken on an empty stomach with a small amount of water.
If stacking
Semaglutide is typically used as a standalone weight management therapy. If using with other diabetes medications, especially insulin or sulfonylureas, doses of those medications may need to be reduced to prevent low blood sugar. Always coordinate with your healthcare provider.
Adjusting Your Dose
Increase if
- +You've tolerated the current dose for 4+ weeks without significant GI issues
- +Weight loss has plateaued and you haven't reached target dose
- +Blood sugar targets aren't being met (for diabetes patients)
- +Your healthcare provider recommends progression based on your response
Decrease if
- -Nausea, vomiting, or diarrhea are severe and persistent
- -You're unable to eat enough to maintain basic nutrition
- -You experience signs of dehydration from GI symptoms
- -Side effects significantly impact your quality of life
Signs of right dose
- ✓Steady weight loss of 1-2 pounds per week
- ✓Feeling satisfied with smaller portions
- ✓Reduced food cravings and thoughts about food
- ✓Manageable or no GI side effects
Dosing Calculator
Calculate Your Exact Dose
Amount to Draw
10
units
Suitability
Is this
right for me?
Best For
People with Obesity Seeking Significant Weight Loss
If your BMI is 30 or higher (or 27+ with weight-related health conditions), semaglutide is currently one of the most effective non-surgical weight loss options available. Clinical trials show average weight loss of 15% of body weight—that's 30+ pounds for someone starting at 200 pounds.
Those Who've Struggled with Diet and Exercise Alone
Semaglutide works by changing the biological signals that drive hunger and cravings. If you've tried to lose weight through willpower alone and found yourself constantly battling hunger, this medication addresses that underlying biology rather than just telling you to eat less.
People with Type 2 Diabetes Needing Better Control
Originally developed for diabetes, semaglutide excellently controls blood sugar while also promoting weight loss—addressing two major health concerns simultaneously. It can often allow people to reduce or eliminate other diabetes medications.
Individuals at High Cardiovascular Risk
The SELECT trial proved that semaglutide reduces heart attacks, strokes, and cardiovascular death by 20% in people with obesity and existing heart disease—even without diabetes. It's one of the few weight loss medications proven to improve hard cardiovascular outcomes.
Consider Alternatives If
Who Should Avoid
Do not use if
- ×You or a family member has had medullary thyroid carcinoma (MTC)—semaglutide caused thyroid tumors in rodents
- ×You have Multiple Endocrine Neoplasia syndrome type 2 (MEN2)—increases thyroid cancer risk
- ×You've had a serious allergic reaction to semaglutide or any GLP-1 medication
- ×You currently have or recently recovered from pancreatitis—GLP-1 drugs may increase risk
- ×You are pregnant or trying to become pregnant—stop semaglutide at least 2 months before conception
- ×You are breastfeeding—it's unknown if semaglutide passes into breast milk
Use with caution if
- !You have a history of gallbladder disease or gallstones—rapid weight loss increases gallstone risk
- !You have diabetic retinopathy—rapid blood sugar improvement can temporarily worsen eye problems
- !You take insulin or sulfonylureas—doses may need reduction to prevent hypoglycemia
- !You have severe GI disorders like gastroparesis—semaglutide further slows stomach emptying
- !You have a history of depression or suicidal thoughts—monitor mood changes
- !You have kidney disease—GI side effects can cause dehydration that worsens kidney function
Administration
How do I
use it?
Reconstitution
What you need
- •Pre-filled semaglutide pen (Ozempic or Wegovy)—no mixing required
- •Pen needles (usually provided or prescribed separately)
- •Alcohol swabs for injection site cleaning
- •Sharps container for safe needle disposal
Injection
Route
Subcutaneous injection (into the fatty tissue just under the skin)—quick, relatively painless, and can be self-administered at home
Best sites
- •Abdomen (stomach area)—at least 2 inches from belly button, most popular site
- •Front of thighs—middle section works best
- •Upper arm—outer area, may need assistance
Technique
- 1.Remove pen cap and attach a new needle—never reuse needles
- 2.Clean injection site with alcohol swab and let it air dry
- 3.If using a new pen, prime it according to package instructions
- 4.Dial your prescribed dose on the pen
- 5.Pinch skin at injection site and insert needle straight in (90-degree angle)
- 6.Press and hold the dose button until the dose counter shows 0
- 7.Keep the button pressed and count slowly to 6 before removing needle
- 8.Remove needle, dispose in sharps container, and replace pen cap
Storage
Signs of degradation
Sample Daily Schedule
Safety
Is it
safe?
Safety Profile
Semaglutide has been studied in over 20,000 participants across multiple large clinical trials, making it one of the most thoroughly researched weight loss medications available. The FDA approved it after rigorous review of safety data. While GI side effects are common (especially early on), serious side effects are rare. The SELECT trial showed it actually reduces cardiovascular events, adding a safety benefit beyond just weight loss.
The safety profile is supported by multiple Phase 3 trials including STEP 1-4 (weight loss) and SELECT (cardiovascular outcomes), with follow-up extending to nearly 4 years. Long-term studies continue, and post-marketing surveillance actively monitors for rare adverse events. The thyroid tumor signal seen in rodents has not been confirmed in humans after years of widespread use.
Common Side Effects
Experienced by some users
Nausea
The most frequently reported side effect, affecting about 44% of users at higher doses. Usually worst during the first few weeks and when increasing doses, then typically improves significantly.
Management: Eat smaller meals, avoid fatty or fried foods, stay upright after eating, and consider ginger or peppermint tea. The slow dose escalation protocol specifically minimizes this. If severe, your doctor may slow the dose increases.
Constipation or Diarrhea
GI motility changes are common as semaglutide slows stomach emptying. Some people experience constipation, others diarrhea, and some alternate between both.
Management: Stay well hydrated, increase fiber intake gradually, and maintain physical activity. Over-the-counter remedies like stool softeners (for constipation) or anti-diarrheals can help. Symptoms usually improve over time.
Decreased Appetite
This is actually how semaglutide works—it's a feature, not a bug. You'll naturally want to eat less and feel full faster. Some people find this dramatic enough that they forget to eat.
Management: While reduced appetite is the goal, make sure you're still eating regular nutritious meals. Focus on protein and vegetables at each meal. Skipping meals entirely can lead to muscle loss and nutritional deficiencies.
Vomiting
About 24% of users experience vomiting, especially during dose increases. Like nausea, it's typically transient and improves as your body adjusts.
Management: Eat bland foods, avoid lying down after meals, and stay hydrated. If vomiting is frequent, contact your healthcare provider—they may recommend staying at the current dose longer before increasing.
Less Common
- •Gallbladder Problems
- •Hair Loss (Telogen Effluvium)
These typically resolve with continued use or dose adjustment.
Stop and Seek Help If
- ×Severe or persistent nausea and vomiting that prevents adequate nutrition despite dose adjustments
- ×Signs of pancreatitis—severe abdominal pain radiating to the back
- ×Allergic reaction—rash, itching, swelling, difficulty breathing
- ×Signs of thyroid tumors—neck lump, hoarseness, trouble swallowing
- ×Pregnancy or planning to become pregnant (stop at least 2 months before conception)
- ×Severe kidney problems or dehydration from GI symptoms
- ×Your healthcare provider recommends discontinuation
Semaglutide is a prescription medication that should only be started, adjusted, or stopped under medical supervision. This information is educational and does not replace professional medical advice. Stopping suddenly is generally safe, but discuss any changes with your healthcare provider.
Interactions
With other peptides
- !Never combine GLP-1 medications—they work through the same mechanism and combining would increase side effects without additional benefit.
- ✓No direct interaction data exists. BPC-157 is sometimes used for GI healing, which could theoretically help with semaglutide's GI side effects, but this is speculative.
- ✓Limited interaction data. Some users combine them, but this should be done under medical supervision as both can affect glucose metabolism.
With medications
- !Insulin - Semaglutide enhances insulin's blood sugar-lowering effect. Insulin doses typically need to be reduced 20-50% when starting semaglutide to prevent hypoglycemia. Work closely with your doctor.
- !Sulfonylureas (glipizide, glyburide) - High risk of hypoglycemia when combined. Sulfonylurea dose usually needs reduction. Monitor blood sugar closely.
- ✓Oral Contraceptives - Semaglutide's effect on gastric emptying may affect absorption of oral medications. Consider taking birth control at a consistent time relative to meals, or discuss alternative contraception.
- ✓Warfarin - May affect warfarin absorption and metabolism. More frequent INR monitoring recommended when starting or changing semaglutide doses.
- ✓Levothyroxine - Take thyroid medication on an empty stomach as usual. Semaglutide shouldn't significantly affect absorption if taken at different times.
With supplements
- ✓Vitamin B12 - Long-term GLP-1 use may reduce B12 absorption. Consider B12 supplementation, especially if you've been on semaglutide for over a year.
- ✓Fiber Supplements - Can help manage constipation from semaglutide. Start slowly to avoid worsening GI symptoms. Psyllium husk is a good option.
- ✓Protein Supplements - Helpful for ensuring adequate protein intake when appetite is reduced. Aim for at least 60-80g protein daily to preserve muscle mass during weight loss.
- ✓Probiotics - May help with GI side effects. Some users find them helpful for digestive comfort during semaglutide therapy.
Effectiveness
Does it
work?
Evidence Level
Strong human trials
What to Expect
Weeks 1-4 (0.25mg dose)
What you might notice
- •Mild nausea, especially after eating larger meals
- •Possibly feeling full slightly faster than usual
- •Minimal to no weight loss yet—this is the adjustment phase
- •Some people feel nothing at this dose, which is completely normal
What's normal
- •GI symptoms that come and go
- •Still feeling hungry between meals
- •Weight staying roughly the same
- •Getting used to the injection routine
What's next
- →After 4 weeks, increase to 0.5mg
- →Continue eating normally—don't force portion changes yet
- →Establish your weekly injection routine
Weeks 5-12 (0.5-1.0mg doses)
What you might notice
- •Noticeably reduced appetite and food thoughts
- •Feeling full on smaller portions
- •Weight loss beginning—typically 2-4 pounds in first month at effective doses
- •GI side effects may temporarily increase with each dose increase, then improve
What's normal
- •Nausea for a few days after dose increases
- •Smaller meals feeling satisfying
- •Early weight loss, though amounts vary widely between people
- •Reduced interest in snacking or large portions
What's next
- →Continue gradual dose increases every 4 weeks
- →Start focusing on protein-rich, nutrient-dense foods
- →Notice how your relationship with food is changing
Weeks 13-20 (1.7-2.4mg doses)
What you might notice
- •Significant appetite suppression—may need reminders to eat
- •Steady weight loss of 1-2 pounds per week
- •Food cravings much more manageable
- •GI symptoms typically stabilizing at this point
What's normal
- •Eating 30-50% less than before without feeling deprived
- •Less interest in formerly tempting foods
- •Clothes fitting looser, physical changes becoming visible
- •Improved energy as weight comes off
What's next
- →Reach and maintain the 2.4mg dose for ongoing weight management
- →Focus on building sustainable eating habits
- →Add or increase physical activity as comfortable
Months 6-12 and beyond
What you might notice
- •Approaching or reaching weight loss goals (average 15% of starting weight)
- •Metabolic improvements visible on lab work
- •New relationship with food and eating habits established
- •Side effects typically minimal or absent at this stage
What's normal
- •Weight loss slowing as you approach a new steady state
- •Maintaining reduced appetite at the 2.4mg dose
- •Lab improvements in blood sugar, cholesterol, inflammation markers
- •Needing to update wardrobe multiple times
What's next
- →Continue maintenance therapy—weight typically returns if medication is stopped
- →Work with your doctor on long-term plan
- →Focus on lifestyle habits that support maintaining your progress
Signs It's Working
Appetite and Eating Behavior
- ✓Feeling satisfied with smaller portions
- ✓Fewer food cravings, especially for sweets and fatty foods
- ✓Reduced 'food noise'—less constant thinking about food
- ✓Natural tendency to choose healthier options
- ✓No longer feeling controlled by hunger
Weight and Body Composition
- ✓Scale weight consistently trending downward
- ✓Clothes fitting looser, needing smaller sizes
- ✓Visible changes in face, waist, and other areas
- ✓Waist circumference decreasing
- ✓Progress photos showing clear differences
Health Markers (via lab tests)
- ✓Blood sugar levels improving (especially HbA1c for diabetics)
- ✓Blood pressure decreasing toward normal
- ✓Cholesterol panel improving (lower LDL, triglycerides)
- ✓Reduced inflammatory markers (hsCRP)
- ✓Liver enzymes improving if previously elevated
Not Seeing Results?
Common reasons
- •Not at therapeutic dose yet—most weight loss happens at 1.7-2.4mg doses; lower starting doses are for adjustment
- •Not waiting long enough—significant results typically take 3-6 months of consistent use at full doses
- •Eating through the medication—forcing yourself to eat large portions despite feeling full defeats the mechanism
- •Choosing calorie-dense foods—smaller portions of high-calorie foods can still prevent weight loss
- •Underlying metabolic conditions—thyroid disorders, PCOS, or medications like steroids may slow progress
- •Dehydration affecting the scale—make sure you're drinking enough water for accurate weight readings
Key Research
"Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1)"
Wilding JPH, Batterham RL, Calanna S, et al., 2021
Finding: This landmark trial proved semaglutide's effectiveness for weight loss. Participants lost an average of 14.9% of their body weight over 68 weeks (about 33 pounds), compared to just 2.4% with placebo. Over half lost more than 15% of their body weight—results previously only seen with surgery.
View Study"Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT)"
Lincoff AM, Brown-Frandsen K, Colhoun HM, et al., 2023
Finding: This massive trial of 17,604 people proved semaglutide reduces heart attacks, strokes, and cardiovascular death by 20% in people with obesity and heart disease—even without diabetes. This was the first time a weight loss medication showed direct cardiovascular benefits.
View Study"Semaglutide from Bench to Bedside: The Experimental Journey"
Weiskirchen R, Lonardo A, 2025
Finding: This comprehensive review traced semaglutide's development from laboratory discovery to clinical breakthrough, documenting its expanding role beyond diabetes into obesity treatment and metabolic liver disease—cementing its status as a transformative therapy.
View Study"Tirzepatide vs. Semaglutide: Clinical Decision-Making in the GLP-1 Landscape"
Mondoh A, Crotty M, le Roux CW, 2025
Finding: Head-to-head comparisons show both medications are highly effective, with tirzepatide producing somewhat greater weight loss in some studies. However, semaglutide has more long-term safety data and the SELECT cardiovascular outcomes trial supporting its use.
View StudyFrequently Asked Questions