What GLP-1 receptor agonists are
Glucagon-like peptide-1 (GLP-1) is a hormone produced in the gut in response to food intake. Among its effects: it stimulates insulin secretion from the pancreas, suppresses glucagon (which would otherwise raise blood glucose), slows gastric emptying, and signals the brain to reduce appetite. GLP-1 receptor agonists are synthetic molecules that bind to the same receptors as natural GLP-1, producing these effects at a sustained, pharmacological level.
Two molecules are currently available or approved in India:
Semaglutide (a GLP-1 receptor agonist): approved for type 2 diabetes management and, in higher doses, for weight management. Available as a weekly subcutaneous injection (the formulation used in the landmark weight management trials) and as an oral daily tablet for diabetes. Generic versions entered the Indian market in the first quarter of 2026 following patent expiry.
Tirzepatide (a dual GIP/GLP-1 receptor agonist): activates both GLP-1 and GIP (glucose-dependent insulinotropic peptide) receptors. Approved in India for diabetes management. The dual mechanism produces more pronounced effects on weight and glucose than semaglutide alone in head-to-head trial data.
What the evidence shows
The clinical trial data on these medications is among the largest and most consistent in obesity medicine:
In the STEP 1 trial (semaglutide 2.4 mg weekly), participants achieved a mean weight reduction of 14.9% over 68 weeks versus 2.4% in the placebo group. Cardiovascular outcomes trials have demonstrated reductions in major adverse cardiovascular events (MACE) in patients with established cardiovascular disease.
In the SURMOUNT-1 trial (tirzepatide), participants achieved a mean weight reduction of 20.9% at the highest dose over 72 weeks. This is the largest sustained weight reduction documented in any pharmacological trial without surgical intervention.
These are population-level means. Individual responses vary substantially, and discontinuation for side effects — particularly gastrointestinal — occurs in a meaningful proportion of patients.
What your doctor evaluates before prescribing
GLP-1 receptor agonists are not appropriate for every patient presenting with weight concerns. A clinical assessment before prescribing evaluates:
Indication. These medications are indicated for patients with a BMI above 27 kg/m² with at least one weight-related metabolic comorbidity (such as type 2 diabetes, hypertension, dyslipidaemia, or obstructive sleep apnoea), or a BMI above 30 kg/m² regardless of comorbidities. In Indian patients, lower BMI thresholds for metabolic risk are increasingly recognised.
Contraindications. A personal or family history of medullary thyroid carcinoma or MEN type 2 syndrome is a contraindication to GLP-1 receptor agonists. Pancreatitis history warrants careful evaluation. These medications are not used in pregnancy.
Current medications and conditions. These molecules affect gastric emptying, which alters the absorption kinetics of other medications, including oral contraceptives and certain diabetes drugs. A medication reconciliation is part of the pre-prescription evaluation.
Metabolic baseline. A comprehensive metabolic panel — including HbA1c, fasting glucose, lipid panel, liver function, and kidney function — establishes the baseline and guides monitoring.
Expectations and commitment. The evidence is clear that discontinuation leads to weight regain. These medications work while taken; the question of long-term use, and what that means for an individual patient, is part of the informed consent discussion.
The side effect profile patients need to understand
The most common side effects are gastrointestinal: nausea, vomiting, diarrhoea, and constipation, particularly during dose escalation. These are typically self-limiting and managed by slow titration — starting at the lowest dose and increasing monthly. Patients who accelerate titration to achieve faster results typically experience more severe side effects.
Nausea is most prominent in the first four to eight weeks. Most patients who continue through this period see substantial improvement in tolerability.
Gallbladder events (gallstones, cholecystitis) occur at a higher rate in patients on these medications than in the general population — likely related to the rate of weight loss and altered bile composition. This is worth discussing with your doctor.
What these medications do not replace
GLP-1 receptor agonists are not a substitute for evaluating the metabolic causes of weight resistance. A patient who has insulin resistance, hypothyroidism, cortisol dysregulation, or sleep apnoea contributing to weight gain will see better outcomes from a plan that addresses the underlying pathophysiology alongside pharmacological support — not from medication alone.
They are also not appropriate as a shortcut for patients without metabolic indication. The appropriate use of these medications is a clinical decision that must be made in the context of a full metabolic assessment, not in response to demand or social media information.