Quick answer
An injection delivered into the fat layer just below the skin (typically abdomen, thigh, or upper arm). Most GLP-1 medications are subcutaneous because the peptide cannot survive oral digestion.
Full definition
Subcutaneous (SC or SubQ) injection delivers medication into the adipose tissue beneath the dermis using a short, fine needle. SC injection provides slower, more sustained absorption than intravenous or intramuscular routes — ideal for peptide drugs like GLP-1 RAs. Most GLP-1s use pre-filled disposable autoinjectors (Wegovy, Zepbound, Mounjaro pens) or multi-dose pens (Ozempic). Common injection sites are abdomen (avoid 2 inches from navel), front of thigh, or back of upper arm; rotate sites to prevent lipohypertrophy.
Deep dive
Subcutaneous Injection: complete reference
Subcutaneous (SC) injection is administration of medication into the fatty layer beneath the skin (the subcutis), where the drug is gradually absorbed into systemic circulation via local capillaries and lymphatics. SC is the standard route for injectable GLP-1s (Wegovy, Ozempic, Zepbound, Mounjaro, Trulicity, Saxenda) because the absorption profile supports sustained drug levels appropriate for once-weekly or once-daily dosing. Standard injection sites: abdomen (most common — fastest absorption, lowest pain), thigh (front-outer), and upper arm (back). Rotation between sites is recommended to prevent lipohypertrophy (fatty tissue thickening from repeated injections at same site). Modern GLP-1 pens use 4-6mm 32-gauge needles — typically painless after the first 1-2 injections. Pen designs (autoinjectors for Wegovy/Zepbound/Trulicity; dial pens for Ozempic) determine ease of use; many patients prefer the autoinjector form for simplicity. After injection, hold for 5-10 seconds before removing needle for full dose delivery.
- In practice
- Inject Wegovy into the abdomen 2 inches from the belly button — rotate sides each week. The pen click + 5-second hold ensures full dose delivery.
- Clinical context
- SC injection is preferred for sustained pharmacokinetics. Rotate sites; abdomen is fastest-absorbing and standard.
Medications
Subcutaneous Injection is most directly relevant to the following GLP-1 medications:
Related terms
- Autoinjector — A pre-filled, single-use pen device that delivers a fixed dose of medication with the push of a butt…
- Titration — The gradual dose escalation schedule used when starting GLP-1 therapy. Typically increases every 4 w…
- Single-Dose Vial — A small glass container holding one dose of medication, typically drawn into a syringe by the patien…
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References
Glucagon-Like Peptide-1 Receptor Agonists: Mechanisms и Clinical Use (Drucker, Cell Metabolism)(2018)
Tirzepatide GIP/GLP-1 Dual Agonism: Mechanism Review (Lancet Diabetes & Endocrinology)(2021)
GLP-1 Effects on Gastric Emptying: Pharmacology Review (American J Physiology)(2020)
Endocrine Society Clinical Practice Guideline: Pharmacological Management of Obesity(2015)
STEP-1 trial: Once-Weekly Semaglutide in Adults with Overweight or Obesity (Wilding et al., NEJM)(2021)
SURMOUNT-1 trial: Tirzepatide Once Weekly для Treatment of Obesity (Jastreboff et al., NEJM)(2022)
SUSTAIN-6 trial: Semaglutide and Cardiovascular Outcomes (Marso et al., NEJM)(2016)
SURPASS-2 trial: Tirzepatide vs Semaglutide в Type 2 Diabetes (Frias et al., NEJM)(2021)
LEADER trial: Liraglutide and Cardiovascular Outcomes в T2D (Marso et al., NEJM)(2016)