Semaglutide Pharmacokinetics: Half-Life, Bioavailability, and ADME

Semaglutide has a terminal half-life of about 7 days. Subcutaneous semaglutide has approximately 89% absolute bioavailability, reaches maximum concentration in 1 to 3 days, is more than 99% albumin-bound, and has an apparent volume of distribution near 12.5 L. Current official labeling distinguishes the oral products: estimated absolute bioavailability is approximately 0.4% to 1% for Rybelsus tablets and 1% to 2% for Ozempic tablets. Both use SNAC-assisted gastric absorption and reach maximum concentration in about 1 hour. Once semaglutide reaches systemic circulation, the molecule-level elimination profile is similar across routes.

These values describe labeled and published clinical datasets for research comparison. They are not personal-use instructions or dosing recommendations.

Overview

Semaglutide (NNC 0113-0217) is a synthetic 31-amino acid GLP-1 analogue developed by Novo Nordisk. FDA approvals include Ozempic for type 2 diabetes in December 2017 (NDA 209637), oral Rybelsus in September 2019 (NDA 213051), and Wegovy for chronic weight management in June 2021 (NDA 215256). Its pharmacokinetic profile was engineered to overcome the rapid enzymatic degradation and renal clearance that limit native GLP-1 to a plasma half-life of minutes.

The primary human PK evidence includes current FDA prescribing information and dedicated absorption, interaction, and special-population studies including PMID 30565096, PMID 30429357, PMID 29623579, and PMID 25475122.

Molecular Engineering for Extended Half-Life

Native GLP-1 is inactivated within minutes by two mechanisms: N-terminal cleavage by dipeptidyl peptidase-4 (DPP-4) and renal filtration. Semaglutide addresses both through three structural modifications:

1. Aib8 substitution. Alpha-aminoisobutyric acid at position 8 replaces alanine, the DPP-4 recognition residue. This single substitution confers near-complete resistance to DPP-4-mediated inactivation.

2. C18 fatty diacid conjugation via a short linker. A C18 fatty diacid (octadecanedioic acid) is attached to lysine at position 26 through a hydrophilic linker. This provides high-affinity, reversible binding to serum albumin at fatty-acid binding sites, reducing renal clearance and helping protect the peptide from metabolic degradation. The same albumin-binding strategy is used by tirzepatide (C20 fatty diacid) and retatrutide (C18 fatty diacid).

3. Arg34 substitution. Lysine at position 34 of native GLP-1 is replaced by arginine to prevent off-target fatty acid conjugation at that site.

Together these modifications produce a molecule that retains full GLP-1 receptor potency while achieving a plasma half-life of approximately 7 days.

flowchart TD
    A["Subcutaneous Injection\n(abdomen / thigh / upper arm)"] --> B["Lymphatic & capillary\nabsorption\nTmax: 1-3 days"]
    O["Oral tablet\n(label PK study conditions)"] --> P["Gastric absorption\nvia SNAC-mediated\ntranscellular transport\nTmax: ~1 h"]
    B --> C["Systemic Circulation\n(>99% albumin-bound)"]
    P --> C
    C --> D["GLP-1R activation\n(pancreas, gut, CNS)"]
    C --> E["Reversible albumin binding\nreduces clearance\n(sustains t½ ~7 days)"]
    E --> C
    C --> F["Peptide-backbone cleavage\n+ sequential beta-oxidation\nof the fatty-acid side chain"]
    F --> G["Amino acid fragments\n+ fatty acid metabolites"]
    G --> H["Urinary & fecal\nexcretion of metabolites"]
    style C fill:#e8f4f8,stroke:#2196F3
    style E fill:#fff3e0,stroke:#FF9800
    style P fill:#f3e5f5,stroke:#9C27B0

Absorption

Subcutaneous Bioavailability

The mean absolute bioavailability of subcutaneous semaglutide is 89% (NDA 209637, Ozempic prescribing information). This was established in a dedicated bioavailability study comparing SC to intravenous administration. The 89% value is label-derived and substantially higher than the oral formulation because it bypasses the gastric absorption barrier.

Time to Maximum Concentration (Tmax)

Following SC injection, the time to maximum plasma concentration (Tmax) is 1 to 3 days (NDA 209637). The prolonged absorption phase is characteristic of large acylated peptides, which enter the systemic circulation via both capillary and lymphatic routes. The wide Tmax range reflects inter-individual differences in SC tissue depth, local vascularity, and lymphatic flow. This gradual absorption smooths the peak-to-trough concentration ratio over the 7-day dosing interval, contributing to tolerability.

Injection Site Equivalence

The prescribing information confirms equivalent exposure from SC injection in the abdomen, thigh, or upper arm (NDA 209637). Injection site rotation does not require pharmacokinetic considerations.

Dose Proportionality

Semaglutide exposure (Cmax and AUC) increases approximately dose proportionally across the studied subcutaneous dose ranges described in the Ozempic and Wegovy prescribing information.

Steady-State Attainment

Steady-state plasma concentrations are reached after 4 to 5 weeks of repeated weekly exposure, corresponding to 4-5 half-lives. This half-life relationship explains why clinical protocols measured exposure across multi-week intervals rather than after a single administration.

Oral Bioavailability and SNAC Mechanism

Oral semaglutide tablets present a fundamentally different absorption challenge. Peptides administered orally face proteolytic degradation by gastric pepsin, pancreatic peptidases, and intestinal brush-border enzymes, combined with low intrinsic permeability across intestinal epithelium. Native GLP-1 has essentially zero oral bioavailability.

Current official labeling covers two SNAC-containing oral products: Rybelsus tablets at 3 mg, 7 mg, and 14 mg, and Ozempic tablets at 1.5 mg, 4 mg, and 9 mg. The earlier Rybelsus formulation studied in the primary absorption literature was co-formulated with 300 mg SNAC (sodium N-[8-(2-hydroxybenzoyl)aminocaprylate]). The mechanisms, elucidated primarily in a 2018 Science Translational Medicine paper (PMID 30429357, Buckley et al.), are:

• Local pH buffering. SNAC dissolves rapidly and raises gastric pH immediately around the tablet surface, inhibiting pepsin activity in the microenvironment near the drug.
• Transcellular absorption through gastric epithelium. Absorption occurs through gastric wall epithelial cells in the region in direct contact with the dissolving tablet. This was confirmed by pharmacoscintigraphic evidence showing complete tablet erosion in the stomach and a Tmax of approximately 1 hour independent of water volume (PMID 33750044, Baekdal et al.).
• The process is highly localized. The study found complete tablet erosion in the stomach with both tested water volumes. AUC over 24 hours and Cmax were approximately 70% higher with 50 mL than with 240 mL; longer erosion and gastric residence correlated with greater exposure (PMID 33750044). The study did not show a 70% reduction when expressed in the reverse direction.

The current combined Rybelsus and Ozempic tablets prescribing information estimates absolute bioavailability at 0.4% to 1% after Rybelsus tablets and 1% to 2% after Ozempic tablets. The 0.4% to 1% estimate also agrees with the earlier Rybelsus clinical PK study (PMID 30565096, Granhall et al.). These formulation-specific estimates should not be collapsed into a single value for all oral semaglutide tablets.

The plasma half-life of semaglutide tablets remains approximately 7 days in current labeling, a property of the molecule after absorption rather than the route of administration.

Distribution

Volume of Distribution

The mean apparent volume of distribution of semaglutide at steady state (Vss) following SC administration is approximately 12.5 liters (NDA 209637). This is close to plasma volume plus the interstitial fluid of well-perfused compartments, consistent with a predominantly plasma-compartment-restricted molecule. The small Vss reflects tight albumin binding that limits tissue distribution. For comparison, tirzepatide has a Vss of approximately 10.3 L.

Albumin Binding

Semaglutide is greater than 99% bound to plasma albumin (NDA 209637). The C18 fatty diacid binds with high affinity to the fatty acid binding sites on albumin. At this binding fraction, the unbound concentration represents less than 1% of total plasma semaglutide. Reversible albumin binding contributes to the low clearance and long half-life described in the label.

Conditions reducing plasma albumin, such as severe hepatic disease, nephrotic syndrome, or sepsis-associated hypoalbuminaemia, could theoretically increase the free fraction and alter pharmacokinetics. The FDA prescribing information includes a dedicated hepatic impairment PK evaluation to address this.

Central Nervous System and Peripheral Targets

Semaglutide does not freely cross the blood-brain barrier as an intact, albumin-bound large peptide. However, GLP-1 receptors in the area postrema and nucleus tractus solitarius, regions of the brainstem lacking a complete blood-brain barrier, are accessible. Vagal afferent neurons expressing GLP-1 receptors in the portal circulation and gut wall provide an additional CNS signaling route without requiring central drug entry. These pathways mediate the satiety, gastric emptying, and food intake effects that are central to semaglutide’s efficacy in obesity trials (SUSTAIN and STEP programs).

Metabolism

Proteolytic Catabolism

Semaglutide does not undergo cytochrome P450-mediated hepatic metabolism. A 2026 experimental study (PMID 41787929) detected 31 metabolites after incubating semaglutide with liver S9 fractions from five species and after dosing rats. It supports peptide-backbone hydrolysis as an experimental pathway but is not a human mass-balance study. The human label describes metabolism by peptide-backbone cleavage and sequential beta-oxidation of the fatty-acid side chain:

1. Hydrolysis of the peptide backbone. Endopeptidases cleave the 31-amino acid chain into smaller peptide fragments. These are further degraded by exopeptidases to amino acids, which re-enter normal metabolic pools. This is the dominant catabolic route.

2. Beta-oxidation of the C18 fatty diacid. After the fatty acid side chain separates from the peptide backbone, it undergoes standard mitochondrial beta-oxidation to acetyl-CoA units.

Semaglutide-related material is excreted in urine and feces. The Ozempic label reports that approximately 3% of a subcutaneous dose is excreted in urine as intact semaglutide, so parent-drug renal excretion is minor rather than absent.

Drug-Drug Interaction Profile

CYP450 pathway. In vitro studies demonstrate that semaglutide does not inhibit or induce CYP450 enzymes and is not a CYP substrate (NDA 209637). Direct pharmacokinetic drug interactions through the CYP450 system are not expected.

Gastric emptying pathway. GLP-1 receptor activation delays gastric emptying and can affect absorption of co-administered oral drugs. PMID 25475122 specifically tested the combined oral contraceptive ethinyl estradiol/levonorgestrel after subcutaneous semaglutide and found that semaglutide did not reduce its bioavailability. The Ozempic label summarizes additional clinical-pharmacology interaction studies; those data should not be attributed to PMID 25475122.

For oral semaglutide, additional DDI studies (PMID 30945118, PMID 33782832) tested lisinopril, warfarin, digoxin, metformin, levonorgestrel, and ethinyl estradiol. Modest increases in furosemide AUC (28%) and rosuvastatin AUC (41%) were observed, though these were not considered clinically relevant per the prescribing information (NDA 213051).

Elimination and Excretion

Plasma Half-Life

The elimination half-life of semaglutide is approximately 7 days (168 hours) for both SC and oral formulations (NDA 209637; NDA 213051). This was derived from population pharmacokinetic modeling of data pooled across multiple clinical studies. The 7-day half-life means:

• Repeated weekly SC exposure provides continuous receptor coverage throughout the modeled interval, with a trough-to-peak ratio that remains pharmacologically relevant.
• Repeated daily oral exposure, despite the low and variable bioavailability, still maintains measurable plasma concentrations given the week-long elimination phase.
• After discontinuation of once-weekly SC semaglutide, plasma concentrations fall to <5% of steady-state trough within approximately 5 weeks.

Apparent Clearance

The apparent clearance of semaglutide following SC administration is approximately 0.05 L/h (NDA 209637). The label directly reports a terminal half-life of approximately one week; a terminal half-life should not be reconstructed from apparent volume and clearance without the underlying compartment model.

Renal Elimination

Renal excretion is not the principal elimination route for intact semaglutide. The Ozempic label reports that approximately 3% of a dose is recovered in urine as intact drug, while semaglutide-related material is excreted in both urine and feces. The prescribing-information datasets report no clinically meaningful renal-impairment effect on exposure (NDA 209637; NDA 213051). For oral semaglutide specifically, Granhall et al. (PMID 29623579) conducted a dedicated PK study enrolling 71 subjects across renal-function categories including end-stage renal disease and haemodialysis. The geometric mean half-life was 152-165 hours across groups. Semaglutide was not detected in urine in all but one participant in that study.

Hepatic Elimination

The liver participates in peptide catabolism but is not the sole elimination organ. Hepatic impairment did not produce a clinically relevant change in semaglutide pharmacokinetics in the prescribing-information dataset (NDA 209637; NDA 213051).

Special Populations

Body Weight

Body weight is a covariate in population PK models for semaglutide. Larger participants have higher apparent volume of distribution, which modestly reduces exposure at a given studied dose. Population PK analyses reported that this covariate did not materially alter exposure-response interpretation across weight categories in the STEP program (NCT03548935 for STEP 1).

Age, Sex, Race, and Ethnicity

Population PK analyses across the SUSTAIN and PIONEER programs showed no clinically relevant effects of age, sex, race, or ethnicity on semaglutide pharmacokinetics (NDA 209637; NDA 213051).

Pediatric Patients

For subcutaneous semaglutide, population PK modeling (PMID 41906858, Strathe et al., 2026) confirmed that modelled semaglutide concentrations over 68 weeks were similar between adolescents and adults, with body weight as the main covariate influencing exposure.

Oral Formulation: Meal Timing and Water Volume Effects

Because oral semaglutide depends on prolonged gastric contact between the tablet and gastric mucosa, administration conditions in the FDA label and PK studies substantially influence exposure:

• Fasted-state administration, separated from the first food, drink, or other medication of the day, produced higher exposure than fed-state administration.
• Lower water volumes maintained longer gastric contact time; larger water volumes accelerated gastric emptying and reduced absorption.
• Co-administration with other beverages or food led to substantially reduced bioavailability in the label-derived PK dataset (NDA 213051).

These observations describe why oral semaglutide has a distinct PK profile from subcutaneous semaglutide. They are not presented as patient instructions or personal-use guidance.

Steady-State Accumulation

With a 7-day terminal half-life, repeated weekly exposure produces a steady-state accumulation ratio of approximately 2-fold relative to a single exposure. Steady state is reached after approximately 4-5 half-lives. At steady state, trough concentrations remain measurable throughout the weekly interval, which explains the molecule-level PK rationale for long-interval subcutaneous study designs.

flowchart LR
    A["Single exposure"] --> B["Repeated exposure\nacross successive half-lives"]
    B --> C["Accumulation phase\n~4-5 half-lives"]
    C --> D["Steady state\nCmax/Cmin ratio\n~1.5-2x"]
    style D fill:#e8f5e9,stroke:#4CAF50

Comparative PK Summary

Summary Table

Key References

1. FDA labeling: Ozempic (semaglutide), NDA 209637. Sections 12.1-12.3.

2. FDA labeling: Rybelsus and Ozempic tablets (semaglutide). Section 12.3 distinguishes estimated absolute bioavailability for the two oral products.

3. FDA labeling: Wegovy (semaglutide), NDA 215256. Sections 12.1-12.3.

4. Buckley ST, Bækdal TA, Vegge A, et al. “Transcellular stomach absorption of a derivatized glucagon-like peptide-1 receptor agonist.” Sci Transl Med. 2018 Nov 14;10(467):eaar7047. PMID 30429357. DOI 10.1126/scitranslmed.aar7047.

5. Granhall C, Donsmark M, Blicher TM, et al. “Safety and Pharmacokinetics of Single and Multiple Ascending Doses of the Novel Oral Human GLP-1 Analogue, Oral Semaglutide, in Healthy Subjects and Subjects with Type 2 Diabetes.” Clin Pharmacokinet. 2019 Jun;58(6):781-791. PMID 30565096. DOI 10.1007/s40262-018-0728-4.

6. Granhall C, Søndergaard FL, Thomsen M, et al. “Pharmacokinetics, Safety and Tolerability of Oral Semaglutide in Subjects with Renal Impairment.” Clin Pharmacokinet. 2018 Dec;57(12):1571-1580. PMID 29623579. DOI 10.1007/s40262-018-0649-2.

7. Baekdal TA, Donsmark M, Hartoft-Nielsen ML, et al. “Relationship Between Oral Semaglutide Tablet Erosion and Pharmacokinetics: A Pharmacoscintigraphic Study.” Clin Pharmacol Drug Dev. 2021 May;10(5):454-464. PMID 33750044. DOI 10.1002/cpdd.880.

8. Kapitza C, Nosek L, Jensen L, et al. “Semaglutide, a once-weekly human GLP-1 analog, does not reduce the bioavailability of the combined oral contraceptive, ethinylestradiol/levonorgestrel.” J Clin Pharmacol. 2015 May;55(5):497-504. PMID 25475122. DOI 10.1002/jcph.443.

9. Bækdal TA, Borregaard J, Hansen CW, et al. “Effect of Oral Semaglutide on the Pharmacokinetics of Lisinopril, Warfarin, Digoxin, and Metformin in Healthy Subjects.” Clin Pharmacokinet. 2019 Sep;58(9):1193-1203. PMID 30945118. DOI 10.1007/s40262-019-00756-2.

10. Jordy AB, Albayaty M, Breitschaft A, et al. “Effect of Oral Semaglutide on the Pharmacokinetics of Levonorgestrel and Ethinylestradiol in Healthy Postmenopausal Women and Furosemide and Rosuvastatin in Healthy Subjects.” Clin Pharmacokinet. 2021 Sep;60(9):1171-1185. PMID 33782832. DOI 10.1007/s40262-021-01003-3.

11. Cong Y, Tang C, Li Z, et al. “Metabolite Profiling and Identification of Semaglutide in Liver S9 Across Species and Rat Plasma.” Biomed Chromatogr. 2026 Apr. PMID 41787929. DOI 10.1002/bmc.70049.

12. Strathe A, Bomberg EM, Jensch G, et al. “Efficacy, Safety and Pharmacokinetics of Semaglutide 1.7 mg for Obesity Treatment in Adolescents: A Model-Informed Drug Development Approach.” Diabetes Obes Metab. 2026 Mar 30. PMID 41906858.

13. Nordell P, Jansson-Löfmark R, Gennemark P, et al. “Systemic Pharmacokinetic Principles of Therapeutic Peptides.” Clin Pharmacokinet. 2026 Apr. PMID 41661442.

This pharmacokinetic reference is for research and informational use only. It is not medical advice, a dosing guide, or a substitute for the current prescribing information and advice from a licensed clinician.

See also

More on Semaglutide:

• Semaglutide research overview

Related peptide family:

• GLP Family

Pathway context:

• Incretin Axis (GLP-1, GIP)

Head-to-head comparisons:

• Semaglutide vs Cagrilintide
• Semaglutide vs Retatrutide