The two-tier system
TGA guidelines use a two-tier BMI threshold:
BMI ≥30 (obesity)
If your BMI is 30 or above, you're eligible for weight loss medication without needing any additional health conditions. This applies to all TGA-approved medications: Wegovy, Mounjaro, Duromine, Contrave, and Xenical.
BMI 27–29.9 (overweight with comorbidity)
If your BMI is between 27 and 29.9, you need at least one weight-related health condition to qualify. Qualifying comorbidities include:
- Type 2 diabetes or pre-diabetes
- High blood pressure (hypertension)
- High cholesterol (dyslipidaemia)
- Obstructive sleep apnoea
- Polycystic ovary syndrome (PCOS)
- Non-alcoholic fatty liver disease
- Cardiovascular disease
- Osteoarthritis (weight-bearing joints)
Your prescribing doctor will assess whether your specific conditions qualify.
BMI thresholds for specific populations
The standard BMI thresholds may be lowered for certain populations who carry higher health risks at lower BMIs:
- Asian populations: BMI ≥27.5 (obesity) or ≥25 (with comorbidity)
- Aboriginal and Torres Strait Islander peoples: May qualify at lower thresholds — discuss with your doctor
These adjusted thresholds reflect evidence that these populations develop metabolic complications at lower BMIs than the general population.
Eligibility by medication
| Medication | BMI requirement | Age | Duration | Special notes |
|---|---|---|---|---|
| Wegovy | ≥30 or ≥27+comorbidity | 12+ | Long-term | Also approved for CV risk reduction |
| Mounjaro | ≥30 or ≥27+comorbidity | 18+ | Long-term | Also approved for type 2 diabetes |
| Duromine | ≥30 or ≥27+comorbidity | 12+ | 12 weeks max | Schedule 8 controlled substance |
| Contrave | ≥30 or ≥27+comorbidity | 18+ | Long-term | Not with opioids or seizure disorders |
| Xenical | ≥30 or ≥27+comorbidity | 18+ | Long-term | 60mg available OTC without prescription |
What will your doctor check?
During your consultation (whether GP or telehealth), the doctor will typically assess:
- BMI calculation: Your current height and weight to calculate BMI
- Weight history: Previous weight loss attempts and outcomes
- Health conditions: Any weight-related comorbidities and other medical conditions
- Medications: Current medications and potential interactions
- Contraindications: Conditions that would make certain medications unsafe (pregnancy, thyroid cancer history, eating disorders, etc.)
- Expectations: Your weight loss goals and understanding of the treatment
Be honest and thorough — this helps the doctor prescribe the right medication at the right dose.
What if my BMI is under 27?
If your BMI is below 27, prescription weight loss medication is generally not indicated under current TGA guidelines. Your doctor may recommend lifestyle modifications (diet, exercise, behavioural support) as first-line treatment.
The only exception is Xenical at the 60mg OTC dose (Alli), which doesn't require a BMI threshold but produces modest results (3–5% weight loss).
What if I've been refused?
Being refused by one doctor doesn't mean you're not eligible. Some GPs are unfamiliar with newer weight loss medications or may have personal views about prescribing them. If you believe you meet the criteria:
- Seek a second opinion from another GP
- Try a telehealth provider that specialises in weight management
- Ask the doctor to explain specifically why you were refused