Monitoring Patients
on GLP-1 Agonists
A Practical Guide for General Practitioners
By Associate Professor Chris Barnes
Published September 2026
GLP-1 receptor agonists represent a major advance in the management of obesity and type 2 diabetes, delivering significant weight loss, improved glycaemic control and cardiovascular benefit.1,2
As use expands into primary care, general practitioners (GPs) are central to initiating and monitoring therapy. However, these benefits are accompanied by important considerations, including reduced nutritional intake, gastrointestinal side effects, and rare complications such as pancreatitis and gallbladder disease.3,4
In parallel, there is increasing use of unregulated GLP-1 products, often sourced online or marketed as “GLP-1 peptides,” which may be ineffective or unsafe. This further reinforces the role of GPs in guiding evidence-based care.
Pathology testing is therefore critical, not only for safety monitoring but also as a structured tool to support patient engagement and optimise outcomes. Emerging real-world evidence highlights that adherence to GLP-1 therapy is highly variable, with discontinuation commonly driven by cost, side effects and inadequate support structures.5
GLP-1 Pathway
The Role of the General Practitioner
GPs provide longitudinal care and are best placed to monitor effectiveness and tolerability, detect complications early, identify nutritional deficiencies, and counsel patients on safe, regulated therapies.
Importantly, pathology testing can be used as an engagement tool, helping to reinforce adherence, provide objective feedback on progress, support shared decision-making and identify early risks and intervene when necessary. This positions pathology as both a clinical and behavioural tool, supporting improved outcomes.
Recommended Laboratory Investigations
Baseline Assessment
Prior to initiation, establish baseline metabolic and nutritional status. Recommended baseline tests:
| Baseline investigations | ||
|---|---|---|
| • HbA1c / fasting glucose • Renal function (U&E, eGFR) • Liver function tests | • Thyroid function (TSH ± fT4) • Iron studies • Vitamin B12 / folate | • Lipid profile • Vitamin D / calcium |
Nutritional Monitoring During Weight Loss
Reduced intake increases the risk of micronutrient deficiency, particularly with rapid weight loss (>5–10%). Recommended monitoring:
| Early Phase Monitoring (rapid weight loss): | Maintenance Phase (6-12 monthly): | Earlier testing if symptomatic: |
|---|---|---|
| • FBC • Iron studies • B12 / folate • Vitamin D / calcium | • Repeat “Early Phase Monitoring” ± albumin | • Fatigue • Hair loss • Dizziness |
Monitoring for Pancreatitis
Pancreatitis is rare but important.4 Test if the symptoms below are present. If lipase is elevated, stop therapy and manage urgently.
| Symptoms | Pathology Monitoring |
|---|---|
| • Persistent epigastric pain • Radiating back pain • Nausea/vomiting | • Serum lipase (preferred) • Serum amylase |
Gallbladder and Hepatobiliary Monitoring
Rapid weight loss increases gallstone risk.3 Investigate for the following symptoms:
| Symptoms | Pathology Monitoring |
|---|---|
| • RUQ pain • Post-prandial symptoms • Abnormal LFTs | • LFTs (ALP, GGT) • Ultrasound if indicated |
Integrating Pathology into Practice
A structured approach is beneficial for patient investigations, consisting of baseline testing, maintenance monitoring (6-12 months) and symptom-triggered testing. Pathology can also be used proactively to track progress, reinforce adherence, detect early complications and reduce treatment-related risk. This enables pathology to support health benefits while minimising adverse outcomes.
Conclusion
GLP-1 agonists are transforming obesity care, with GPs at the centre of safe implementation. This role is increasingly important given the rise of unregulated GLP-1 products. Pathology testing underpins effective care by enabling baseline risk assessment, early and ongoing nutritional monitoring, detection of complications, and patient engagement and adherence. A structured, evidence-informed approach allows GPs to maximise benefit while minimising harm.
References
- Wilding JPH, Batterham RL, Calanna S, Davies M, Van Gaal LF, Lingvay I, et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384(11):989–1002.
- Davies MJ, Aroda VR, Collins BS, Gabbay RA, Green J, Maruthur NM, et al. Management of hyperglycaemia in type 2 diabetes. Diabetologia. 2022;65(12): 1925–66.
- MA, Meier JJ. Management of Endocrine Disease: Are all GLP-1 agonists equal in the treatment of type 2 diabetes? Eur J Endocrinol. 2019;181(6):R211-R34.
- Marso SP, Daniels GH, Brown-Frandsen K, Kristensen P, Mann JFE, Nauck MA, et al. Liraglutide and cardiovascular outcomes. N Engl J Med. 2016;375(4):311–22.
- Alex Griffiths Oliver M Shannon Marie Spreckley Kate Austin et al Exploring real-world user experiences of GLP-1 receptor agonist therapy for obesity treatment, and barriers and motivators to adherence medRxiv 2025.12.11.25342052; https://doi.org/10.64898/2025.12.11.25342052
- Mechanick JI, Apovian C, Brethauer S, Garvey WT, Joffe AM, Kim J, et al. Bariatric nutrition guidelines. Endocr Pract. 2019;25(12):1346–59.
About the Author
Associate Professor Chris Barnes
MBBS FRACP FRCPAAssociate Professor Chris Barnes
MBBS FRACP FRCPA- paediatric haematology
- non–malignant haematological conditions including
- thrombosis and bleeding disorders
Associate Professor Chris Barnes joined Clinical Labs in 2016 and is the National Director of Clinical Pathology. Prior to this, he worked as a consultant haematopathologist with Healthscope Pathology from 2009. Chris is a dual-trained clinical and laboratory haematologist, having trained at the Royal Children’s Hospital and the Royal Melbourne Hospital. He also undertook training at The Hospital for Sick Children in Toronto, Canada. He holds a part-time public hospital appointment at the Royal Children’s Hospital, where he serves as the Director of the Henry Ekert Haemophilia Treatment Centre. Chris has extensive clinical research interests and is the principal investigator on eight separate clinical trials based at the Murdoch Children’s Research Institute. He has held numerous leadership positions, including Chair of the Medical Staff Association at the Royal Children’s Hospital and Chair of the Australian Haemophilia Directors Association. He is currently the Chair of the Australian Bleeding Disorders Registry with the National Blood Authority and a Director of Melbourne Haematology and Melbourne Paediatric Specialists. Chris’ focus within Clinical Labs is the national supervision and management of clinical pathology disciplines, including haematology, biochemistry, microbiology and immunopathology.
Related Pages
Diabetes Clinical Evaluation Program
This CPD program helps participants easily manage and provide clinical care for their patients living with diabetes via HbA1c and pathology testing.
What's the Real Measure of Vitamin B12 Deficiency?
Associate Professor Chris Barnes reviews the limitations of serum and Active B12 testing and outlines a clinically aligned approach to detecting functional vitamin B12 deficiency following the 2025 MBS changes.
Investigating Fatigue in Women
Associate Professor Chris Barnes explores modern approaches to diagnosing fatigue in women, offering clinical recommendations to improve patient outcomes.