GLP-1 Dosing and Injection Sites Explained

The three approved GLP-1 injection sites are abdomen, front of thigh, and back of upper arm. You pick one area per dose and rotate between them to prevent skin irritation and ensure medication absorbs consistently. The abdomen is most popular site because it has a reliable fat layer and is easy to reach. Inject at least two inches from your belly button, avoid scars and moles, and insert needle at a 90-degree angle into fatty tissue beneath skin.

If you're new to GLP-1 drugs and trying to figure out dosing schedules, where to inject, how to convert between different drugs, or what to do when you miss a dose, this article covers all of it. Every GLP-1 drug follows a similar pattern: start low, increase gradually, inject subcutaneously, and rotate your sites. The specific doses and timelines differ by drug. Let's go through each one.

Where are GLP-1 injection sites?

GLP-1 drugs are injected subcutaneously, which means into fat layer just beneath your skin. Not into muscle. Not into a vein. The fat layer absorbs medication slowly and releases it into your bloodstream over days, which is how weekly injections work.

The abdomen is most commonly recommended spot. Choose any fatty area on front of your stomach between bottom of your ribs and top of your hip bone. Stay at least two inches from your belly button. The fat layer here tends to be even, which helps drug absorb smoothly.

The front and outer portion of thigh is second option. Aim for middle third, roughly halfway between your knee and your hip. Avoid inner thigh. This site works well if you prefer sitting down or don't want to lift your shirt.

The back of upper arm is third approved site. Choose a spot between your shoulder and your elbow on outer or back side. This area is harder to reach on your own, so some people need help from a family member or partner.

A few things matter regardless of which site you choose. Clean area with an alcohol swab and let it air dry. Pinch a fold of skin. Insert needle at 90 degrees (or 45 degrees if you're lean and there's less fat). Push plunger slowly. Hold for five to ten seconds before withdrawing. Don't rub spot afterward.

Rotating sites is not optional. Using same exact spot repeatedly can cause small rubbery lumps called lipohypertrophy. These lumps change how medication absorbs, which can make your doses unpredictable. Move at least one inch from your last injection and switch between body areas. A simple system: abdomen one week, right thigh next, left thigh after that, upper arm if you have help.

We cover injection sites in much more detail, including rotation strategies and troubleshooting, in GLP-1 injection sites guide.

What are dosing schedules for each GLP-1 drug?

Every GLP-1 drug starts at a low dose and increases gradually. This process is called titration. It reduces nausea and other GI side effects that would hit hard if you started at full dose.

Semaglutide (Wegovy) starts at 0.25 mg weekly for four weeks, then 0.5 mg, then 1.0 mg, then 1.7 mg, then maintenance dose of 2.4 mg. The entire escalation takes about 16 to 20 weeks. For a complete breakdown of each step, see Ozempic dosage chart.

Tirzepatide (Zepbound, Mounjaro) starts at 2.5 mg weekly for four weeks, then increases by 2.5 mg every four weeks. The available steps are 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. Not everyone needs to reach 15 mg. Some people do well at 10 mg or 12.5 mg. The tirzepatide dosage chart walks through each dose and what it delivers. If you're curious about maximum, we cover that in highest dose of tirzepatide.

Liraglutide (Saxenda) is a daily injection. It starts at 0.6 mg and increases by 0.6 mg each week until you reach maintenance dose of 3.0 mg. Because it's daily rather than weekly, titration is faster but injection routine is more frequent.

Oral semaglutide (Wegovy pill) starts at 3 mg daily and steps up to 7 mg, then 14 mg, then 25 mg. Each step lasts at least four weeks. The pill has to be taken on an empty stomach with no more than 4 ounces of water, and you can't eat or take other medications for 30 minutes afterward.

How do you convert doses between different GLP-1 drugs?

There is no direct milligram to milligram conversion between GLP-1 drugs because they are different molecules that bind to receptor with different potencies. You can't simply say "2.4 mg of semaglutide equals X mg of tirzepatide."

What doctors use instead is clinical equivalence, matching approximate level of appetite suppression and weight loss between drugs. Based on trial data, semaglutide 2.4 mg (Wegovy) produces roughly similar weight loss to tirzepatide 10 mg. Tirzepatide at 15 mg produces more weight loss than semaglutide at any dose.

If you're switching from one drug to another, your doctor will typically start you at a mid-range dose of new drug rather than starting from scratch. The semaglutide to tirzepatide conversion article covers specific crossover approach.

We break down conversion tables for every drug pairing in GLP-1 dose conversion chart.

How many units are in each dose?

This question comes up because some people use compounded GLP-1 medications from pharmacies that provide vials and syringes rather than pre filled pens. In that case, you need to know how to measure your dose in units on an insulin syringe.

The answer depends on concentration of medication. For example, how many units is 2.5 mg of tirzepatidedepends on whether your vial is compounded at 5 mg/mL, 10 mg/mL, or another concentration. The math changes every time concentration changes. If you're using a pre-filled pen (Ozempic, Wegovy, Mounjaro, Zepbound), pen handles dosing for you and you don't need to calculate units.

When is best time to inject?

For weekly injections (semaglutide, tirzepatide), you choose one day per week and stick with it. The time of day doesn't matter. You can inject in morning or at night, with or without food. What matters is consistency: same day every week.

Some people prefer injecting in evening because any nausea from dose increase happens overnight while they sleep. Others prefer morning because it fits their routine. There is no clinical evidence that one time of day works better than another.

Best time of day to take Mounjaro goes deeper into timing question, including how to adjust if your schedule shifts.

For daily injections (liraglutide, oral semaglutide), consistency matters more. Take it at approximately same time each day. Oral semaglutide has additional requirement of an empty stomach and a 30 minute wait before food.

What if you miss a dose or want to take it early?

For weekly semaglutide: if you miss a dose and it's been less than five days since you were supposed to inject, take it as soon as you remember. If it's been five or more days, skip that dose and take next one on your regular day.

For weekly tirzepatide: rule is similar. If it's been less than four days since your scheduled dose, take it. If it's been four or more days, skip it and resume on your regular day.

Taking a dose a day or two early is generally fine. Can you take Mounjaro a day early? Yes. Just don't take two doses within three days of each other. And don't double up to make up for a missed dose.

How should you store GLP-1 medications?

Unopened pens and vials should be stored in refrigerator at 36 to 46 degrees Fahrenheit (2 to 8 degrees Celsius). Don't freeze them. Freezing destroys medication.

Once you start using a pen, it can be kept at room temperature (up to 86 degrees Fahrenheit or 30 degrees Celsius) for a limited time. For semaglutide pens, that window is 56 days. For tirzepatide pens, it's 21 days at room temperature. After that, discard pen even if medication is left inside.

How long does tirzepatide last in fridge covers full storage details, including what to do if a pen has been left out too long.

Let medication come to room temperature for about 30 minutes before injecting. Cold medication stings more. Don't microwave it or run it under hot water to warm it up. Just let it sit on counter.

What about microdosing GLP-1 drugs?

Microdosing is practice of using GLP-1 drugs at doses lower than standard titration schedule, sometimes by starting at sub-therapeutic doses or increasing more slowly. This is not FDA approved and is not in any official prescribing guide. But some doctors use it for patients who are extremely sensitive to side effects or who want a gentler introduction.

The idea is to let body adjust to even smaller amounts of drug before moving into standard dose range. For example, some compounding pharmacies provide tirzepatide in concentrations that allow dosing at 1.0 mg or 1.25 mg, below standard 2.5 mg starting dose.

There isn't strong clinical trial data on microdosing. The available evidence comes from anecdotal reports and small case series. If this approach interests you, we cover details in GLP-1 microdosing chart and guide.

What happens when you reach your goal weight?

Once you've reached your target weight, question becomes whether to stay on same dose, reduce to a lower maintenance dose, or stop entirely. The evidence is clear that stopping GLP-1 drugs leads to weight regain in most people. The appetite and metabolic signals return to their pre treatment levels.

Some doctors explore stepping down to a lower tirzepatide maintenance dose after weight loss. The goal is to find lowest dose that keeps your weight stable with fewer side effects and lower cost. This approach is still being studied, but it's increasingly common in clinical practice.

Your doctor can help you plan a long term strategy based on how your body has responded and what your goals are going forward.