Semaglutide Injection Guide: Weekly Steps

Last reviewed: June 4, 2026

Last updated: June 4, 2026

Written by: Jay Hastings, CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

This article is part of the PlexusDx Education Hub — science-backed guidance on GLP-1 medications, metabolic health, and precision weight management.

Semaglutide injections are administered once per week, making them a convenient option for people managing weight through GLP-1 receptor agonist therapy. The actual injection takes less than 10 seconds, but proper preparation and technique ensure safety and comfort. PlexusDx compounded semaglutide is dispensed from licensed 503A pharmacies and comes with detailed instructions tailored to your specific starting dose.

Preparing Your Semaglutide Injection Site

Before injecting, select an injection site on your abdomen, upper arm, or thigh—areas with adequate fatty tissue underneath the skin. Rotate your injection location each week to prevent lipodystrophy, a condition where repeated injections in the same spot can cause tissue changes. Most patients find the abdomen most convenient because it's easy to access and has consistent subcutaneous depth.

Wash your hands thoroughly with soap and water, then clean your chosen injection site with an alcohol wipe or sterile pad. Allow the area to air-dry completely—injecting through wet alcohol can reduce medication effectiveness and increase discomfort. Remove your semaglutide pen or prefilled syringe from the refrigerator about 15 minutes before use; room-temperature medication is less uncomfortable to inject than cold medication.

Step-by-Step Semaglutide Injection Technique

Hold your semaglutide pen or syringe at a 90-degree angle to your skin, positioning it perpendicular to your body. Pinch the cleaned skin gently between your thumb and forefinger to create a fold of fatty tissue. Insert the needle straight down into the fold with one smooth, confident motion—hesitant movements can increase pain perception.

Once the needle is fully inserted, press the injection button or plunger slowly and steadily until you hear a click or feel resistance, which signals that the full dose has been delivered. Hold the pen or syringe in place for 3-5 seconds after injection to ensure all medication enters the subcutaneous space. Remove the needle at the same 90-degree angle using a quick, direct motion, then apply gentle pressure with a clean gauze pad if needed.

Proper Storage and Handling of Your Medication

Unopened semaglutide pens and syringes from PlexusDx must be stored in a refrigerator between 36°F and 46°F (2°C to 8°C) in their original packaging. Keep your medication away from direct light and heat sources, and never freeze it—freezing damages the medication and makes it unsafe to use. Once you begin using a pen or syringe, it can remain at room temperature (up to 86°F/30°C) for up to 30 days if stored in a cool, dark place.

When traveling, use an insulated medication travel case with cooling packs to maintain the proper temperature range. If your semaglutide freezes or appears cloudy or discolored, discard it immediately and contact PlexusDx for a replacement. Always keep your medication in its original labeled container so you can verify the correct dose and expiration date before each injection.

What to Expect After Your Weekly Injection

Most patients experience minimal discomfort immediately after their semaglutide injection, though slight redness or mild bruising at the injection site is normal and usually resolves within hours. You may notice appetite suppression beginning within 2-4 hours of injection, with peak effectiveness occurring around 48 hours post-injection. Nausea is possible during the first few weeks as your body adjusts, but this typically decreases as your system becomes accustomed to the medication.

If you experience significant pain, swelling, or signs of infection at the injection site, contact your PlexusDx care team immediately. Mild side effects like nausea, constipation, or fatigue are common during the first 4-6 weeks and often improve with dose titration. Your dose may increase over time based on your response and tolerance, but your price remains the same—PlexusDx charges one flat monthly rate regardless of dose level.

Personalization: How Genetic Testing Enhances Your Results

PlexusDx offers the Precision Peptide Genetic Test to identify how your genetic makeup influences your response to semaglutide and other GLP-1 medications. This test examines 14 peptide-regulating pathways and 150+ genetic insights, including variants in GLP1R (rs6923761), GIPR (rs1800437), and MC4R (rs17782313) that directly affect GLP-1 receptor sensitivity. Understanding your genetic profile helps your care team optimize your starting dose and predict your medication response pattern.

Patients with certain genetic variants may benefit from earlier dose escalation or may achieve excellent results at lower doses than expected. The Precision Peptide Genetic Test is available as a $99 add-on after your first month of treatment, giving your body time to adjust while providing valuable data for long-term personalization. This data-driven approach has helped many PlexusDx patients achieve faster weight loss with fewer side effects than standard dosing protocols.

How Your Genetics Influence GLP-1 Response

Not everyone responds to GLP-1 medications the same way. Genetic variants — including GIPR rs1800437, GLP1R rs6923761, FTO rs9939609, and MC4R rs17782313 — influence how your body processes these medications, how much weight you lose, and how you tolerate side effects. PlexusDx maps 14 pathways, 49 peptides, and 150+ genetic insights to match each patient to the right medication, dose, and lifestyle protocol for their biology. The PlexusDx Precision Peptide Genetic Test ($99 add-on after your first month of treatment) gives your provider precise insight into your peptide genetic predispositions before the first prescription is written.

Access Personalized GLP-1 Care Through PlexusDx

PlexusDx offers six prescription GLP-1 protocols to all 50 states — no membership, no insurance required, async intake or live consult. The Semaglutide Injection starts at $149/mo. Medications are dispensed from licensed 503A compounding pharmacies following strict quality and safety standards. Add a Precision Peptide Genetic Test for $99 to personalize your protocol from day one.

Frequently Asked Questions

How often do I inject semaglutide from PlexusDx?

PlexusDx semaglutide is injected once per week, always on the same day. You can inject any day of the week that fits your schedule—Sunday, Monday, or any other day—as long as you maintain a consistent 7-day interval between injections. If you miss a dose, inject within 2 days; if more than 2 days have passed, skip that dose and resume your regul...

What clinical trials support weekly semaglutide dosing?

Large-scale studies including STEP 1, STEP 2, and STEP 4 demonstrated that participants using once-weekly semaglutide achieved 15-22% body weight loss over 68 weeks compared to 2-3% with placebo. Weekly dosing has become the standard because it provides sustained GLP-1 receptor activation, maintains consistent appetite suppression, and simplifie...

How much does PlexusDx semaglutide cost each month?

PlexusDx compounded semaglutide injections start at $149 per month across all three commitment tiers. Your price remains flat regardless of dose level—if your dose increases during treatment, your monthly cost stays the same. PlexusDx accepts HSA and FSA funds and serves all 50 states without requiring insurance or membership fees.

Are there serious side effects I should watch for?

Most semaglutide side effects are mild to moderate and improve within 4-6 weeks, including nausea, constipation, and fatigue. Serious but rare side effects include pancreatitis (severe abdominal pain), gallbladder problems, and signs of thyroid disease. Contact PlexusDx immediately if you experience persistent severe pain, vision changes, or dif...

Can genetic testing predict how well I'll respond to semaglutide?

Yes. PlexusDx Precision Peptide Genetic Test identifies variants in GLP1R, GIPR, FTO, and MC4R genes that influence how your body responds to semaglutide and GLP-1 therapy. Patients with certain variants may need faster dose escalation or may achieve excellent results at lower doses. The test costs $99 as an add-on after your first month and pro...

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