You just took your first injection. Now what? The first week on GLP-1 medication can feel uncertain—you're waiting for something to happen, wondering if it's working, and maybe nervous about side effects.
Here's exactly what to expect, day by day.
Day 1: Injection Day
đź“Ť The Injection Itself
What to expect: Quick pinch. Most people say "that's it?" The needle is thin and short. Many first-timers are surprised how easy it is.
Where to inject: Abdomen (2 inches from belly button), thigh, or back of upper arm. Rotate sites.
How you'll feel: Probably nothing immediately. The medication takes time to build up.
Don't expect dramatic effects on day one. Some people notice subtle fullness at dinner, but most notice nothing different. That's normal.
Days 2-3: Settling In
đź“Ť Early Effects (Maybe)
Appetite: You might notice you're slightly less interested in food. Or you might notice nothing. Both are normal.
Side effects: If you're going to have GI side effects, they often start around day 2-3. Most common: mild nausea, slight queasiness, feeling "off."
Energy: Some people feel slightly tired; others feel no different.
First Week Tips
- Eat smaller meals—don't test your capacity
- Avoid fatty, greasy foods (harder to digest)
- Stay hydrated—water, water, water
- Don't force yourself to eat if not hungry
- Have ginger tea or candies on hand for nausea
Days 4-5: Building Up
đź“Ť Mid-Week Check
Appetite: More likely to notice reduced hunger now. You might realize you forgot to eat lunch. Snacking urges may diminish.
Fullness: Getting full faster at meals. Portions that were normal before feel like too much.
GI status: Side effects may peak around days 3-5 for some people, then start to improve. If you've had no GI issues, you may not get them.
This is often when people have their "whoa" moment—realizing they simply don't want the second helping, or that the food thoughts that used to fill their head are... quieter.
Days 6-7: The New Normal Emerging
đź“Ť End of Week One
What's working: Reduced appetite, earlier fullness, less "food noise." Many people describe a quieting of constant food thoughts.
What you might notice: You're leaving food on your plate. You forgot about the snack drawer. You didn't finish your usual portion.
Scale: You might see 1-3 pounds down—mostly water weight. Don't expect dramatic loss in week one.
Common Week One Questions
"Is it normal to not feel anything?"
Yes. Some people have subtle effects at the starting dose (0.25mg semaglutide or 2.5mg tirzepatide). These are intentionally low doses for adjustment. Effects typically increase as you titrate up.
"Is it normal to feel nauseous?"
Yes—about 40-50% of people experience some nausea, usually mild. It typically peaks in the first few days and improves. Eating smaller, more frequent meals helps.
"Should I force myself to eat?"
Don't force large amounts, but do eat something. Your body needs nutrition. Focus on protein-rich foods when you do eat. Small portions, frequent if needed.
"When do I take my second injection?"
One week from your first. Same day of the week going forward. Set a recurring reminder.
What's NOT Normal
Contact your provider if you experience:
- Severe, persistent vomiting (can't keep fluids down)
- Severe abdominal pain
- Signs of dehydration
- Symptoms of pancreatitis (severe upper abdominal pain radiating to back)
- Allergic reaction symptoms (rash, swelling, difficulty breathing)
Mild GI discomfort is expected. Severe symptoms are not—when in doubt, call your provider.
Managing Side Effects
For Nausea
- Eat slowly and stop when full
- Avoid lying down right after eating
- Ginger (tea, candies, supplements)
- Peppermint tea
- Cold foods sometimes tolerated better than hot
- Avoid strong smells
For Constipation
- Hydrate aggressively
- Fiber-rich foods or supplements
- Movement/walking
- Stool softener or gentle laxative if needed
For Fatigue
- Often improves as body adjusts
- Make sure you're eating enough
- Stay hydrated
- Prioritize sleep
Week One Success Looks Like...
- âś… Completed your first injection without incident
- ✅ Noticed some (or no) appetite changes—both normal
- âś… Managed any GI side effects without emergency
- âś… Stayed hydrated
- âś… Didn't panic about slow effects
- âś… Set your reminder for week two injection
That's it. Week one is about adjustment, not dramatic results. The weight loss comes over months, not days.
Key mindset: Week one is the starting line, not the finish line. You're giving your body time to adjust to a new medication. The significant effects come as you titrate up over the following weeks and months. Be patient.
Looking Ahead
After 4 weeks at the starting dose (assuming you tolerate it), you'll typically increase. Each dose increase may bring stronger appetite suppression—and potentially a brief return of GI adjustment.
Most people notice their most significant appetite changes between weeks 4-12 as they reach effective doses. Your first week is just the foundation.