Starting a GLP-1 medication like semaglutide (Wegovy/Ozempic) or tirzepatide (Mounjaro/Zepbound) is exciting but can feel overwhelming. Knowing what to expect week-by-week helps you prepare, manage side effects, and maximize results.
This guide walks you through exactly what happens in your first 30 days, from your first injection through the initial dose escalation period.
Before Your First Injection
✅ Pre-Start Checklist
- Medical consultation complete: Reviewed medical history, contraindications, goals
- Medication received and stored properly: Refrigerated at 36-46°F
- Injection supplies ready: Alcohol swabs, sharps container
- Baseline measurements taken: Weight, waist circumference, photos (optional)
- Anti-nausea medication prescribed: Ondansetron (Zofran) as backup
- Grocery shopping done: Protein-rich foods, bland options, ginger tea
- Support system informed: Family/friends know you're starting medication
💡 Pro Tip: Set Yourself Up for Success
Schedule your first injection for a Friday evening or Saturday morning. This gives you the weekend to adjust to initial side effects without work obligations. Plan lighter activities and have easy-to-digest foods readily available.
Week 1: The Beginning
Starting Dose
Semaglutide: 0.25mg once weekly (lower than therapeutic dose - for adaptation)
Tirzepatide: 2.5mg once weekly (also sub-therapeutic starter dose)
These low starting doses help your body adapt with minimal side effects. Don't expect significant weight loss yet.
What You'll Likely Experience
- Reduced appetite: 60-70% of patients notice this within 24-48 hours
- Mild nausea: 30-40% experience light nausea, usually manageable
- Feeling full faster: Can only eat 50-70% of normal portion sizes
- Minimal weight loss: 0-3 lbs (mostly water weight at this stage)
- Slight fatigue: Body adjusting to reduced calorie intake
- Possible headache: Usually mild, often dehydration-related
Week 1 Action Items
- Track your side effects in a journal or app
- Drink 80-100oz water daily
- Eat protein-rich, easy-to-digest foods
- Don't force yourself to finish meals if full
- Avoid high-fat, greasy foods
- Get adequate sleep (7-9 hours)
- Take before/after photos for comparison
Week 2: Adaptation
Same Dose (Week 2 of 4 at starting dose)
You'll stay at the same low dose for a full month (4 weeks total). Week 2 is typically when your body starts adapting and side effects may improve slightly.
What You'll Likely Experience
- Side effects stabilizing: Nausea may decrease slightly
- Appetite continues to be reduced: Eating 50-70% of previous intake
- Weight loss begins: 2-5 lbs total from start (realistic range)
- Energy adjusting: May feel slightly low as body adapts to fewer calories
- Digestive changes: Possible constipation or diarrhea as GI adjusts
- Mental clarity about portions: Realizing how much you used to overeat
Week 2 Action Items
- Continue tracking weight 1-2x weekly (not daily - too variable)
- Start establishing meal routine: 4-6 small meals
- Add fiber supplement if experiencing constipation
- Begin light exercise if not already (walking 20-30 min daily)
- Meal prep protein-rich options for the week
- Monitor hydration - urine should be pale yellow
Week 3: Finding Your Rhythm
What You'll Likely Experience
- Side effects improving: 60-70% of patients report nausea decreasing
- New normal emerging: Smaller portions feel routine
- Total weight loss: 3-7 lbs from start (varies by starting weight)
- Increased energy: Body adapting to new calorie intake
- Clothes fitting differently: May notice waistband loosening
- Confidence building: Seeing initial results reinforces commitment
Week 3 Action Items
- Assess which foods work best for you (easy to digest, satisfying)
- Consider starting resistance training (3x weekly recommended)
- Prepare mentally for dose increase next week
- Review side effect management strategies
- Celebrate non-scale victories (energy, mood, clothes fit)
- Schedule follow-up with provider if needed
Week 4: Dose Increase
First Dose Increase
Semaglutide: Increase from 0.25mg to 0.5mg once weekly
Tirzepatide: Increase from 2.5mg to 5mg once weekly
⚠️ Important: Side effects typically worsen temporarily with dose increases, then improve within 1-2 weeks.
What You'll Likely Experience
- Increased nausea: May return or worsen for 3-7 days post-injection
- Stronger appetite suppression: May eat only 40-60% of pre-GLP-1 intake
- Total weight loss: 5-10 lbs from start (end of month 1)
- Possible fatigue increase: Temporary as dose increases
- GI changes: Constipation or diarrhea may occur
- Food aversions: Some foods may suddenly seem unappealing
Week 4 Action Items
- Have anti-nausea medication (Zofran) ready
- Stick to gentle, bland foods for 2-3 days post-injection
- Extra focus on hydration (100oz+ water)
- Reduce exercise intensity if needed - listen to body
- Track your progress: weight, measurements, photos
- Plan for month 2: you're in this for the long haul!
Realistic Weight Loss Expectations: Month 1
| Starting Weight | Typical Month 1 Loss | % of Body Weight |
|---|---|---|
| 200 lbs | 5-10 lbs | 2.5-5% |
| 250 lbs | 6-12 lbs | 2.4-4.8% |
| 300 lbs | 8-15 lbs | 2.7-5% |
| 350 lbs | 10-18 lbs | 2.9-5.1% |
Important Context
- Month 1 is slowest: You're on starter doses (sub-therapeutic)
- Months 2-4 accelerate: Weight loss increases as dose escalates
- Individual variation is huge: Some lose 3 lbs, others lose 15 lbs - both normal
- Water weight first: Initial loss is mostly water, fat loss accelerates later
- Don't compare to others: Your journey is unique
⚠️ Red Flags: When to Contact Provider
- Zero weight loss after 4 weeks (may need dose adjustment)
- Severe side effects preventing daily activities
- Unable to keep down food or water for >24 hours
- Extreme dizziness or fainting
- Severe abdominal pain
- Signs of pancreatitis (severe upper abdominal pain radiating to back)
Common Month 1 Mistakes to Avoid
❌ Not Eating Enough Protein
With appetite suppressed, it's easy to under-eat protein. This accelerates muscle loss. Aim for 30-40g protein per meal, even if portions are small.
❌ Expecting Dramatic First Month Results
You're on starter doses. Expecting 20 lbs in month 1 sets you up for disappointment. Trust the process - results accelerate in months 2-6.
❌ Weighing Daily
Weight fluctuates 2-5 lbs daily due to water, sodium, hormones. Weigh 1-2x weekly maximum, same day/time, for accurate tracking.
❌ Ignoring Hydration
GLP-1s reduce thirst signals. Dehydration causes fatigue, headaches, constipation. Set phone reminders to drink water throughout the day.
❌ Pushing Through Severe Side Effects
If nausea is debilitating, contact your provider. They can prescribe anti-nausea meds or slow escalation. Don't suffer unnecessarily.
The Bottom Line
Month 1 is about adaptation, not dramatic results. You're on starter doses designed to help your body adjust with minimal side effects.
Expect 5-12 lbs weight loss in month 1 (varies by starting weight). This is normal and healthy. Weight loss accelerates significantly in months 2-6 as dose increases.
Side effects peak around week 4 with first dose increase, then improve within 1-2 weeks. Stay consistent with management strategies: small frequent meals, hydration, protein priority, bland foods.
Focus on building sustainable habits: meal routine, exercise schedule, hydration goals, sleep consistency. These habits determine long-term success more than the medication alone.
Month 1 sets the foundation. Be patient, trust the process, and celebrate every positive change - not just the number on the scale.