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Gaining weight without a clear change in diet or exercise habits. May indicate hormonal, metabolic, or medication-related causes.
There are several possible causes. Here are the most common ones:
Underactive thyroid slows metabolism.
You might suspect this if you have:
Many medications cause weight gain.
You might suspect this if you have:
Excess fluid causing rapid weight increase.
You might suspect this if you have:
Hormonal condition in women.
You might suspect this if you have:
Excess cortisol production.
You might suspect this if you have:
Important: This information is for general guidance only and should not be used to self-diagnose. A doctor can properly assess your symptoms and provide appropriate advice.
Call 000 or go to Emergency immediately
When a patient tells me they are gaining weight without eating more, I take it seriously — but I also investigate honestly. Research shows that most people significantly underestimate their caloric intake (by 40-50% on average). That said, genuine unexplained weight gain does occur and has identifiable medical causes. The most common is hypothyroidism, followed by medication side effects (which are vastly underappreciated — many commonly prescribed medications cause 5-10kg of weight gain). PCOS in women is another major cause. The investigation is straightforward: thyroid function, fasting glucose, and in some cases hormone panels. Via telehealth, I can order the appropriate blood tests, review medications for weight-gaining culprits, and provide evidence-based guidance.
Medical certificate guidance: Unexplained weight gain itself rarely requires a certificate, but the underlying cause (hypothyroidism, depression) or associated symptoms (severe fatigue, mobility limitation) may.
All clinical decisions are made by AHPRA-registered doctors following our clinical governance framework. We never automate clinical decisions.
The most common are hypothyroidism, PCOS, medication side effects, insulin resistance, Cushing's syndrome, and fluid retention from heart, liver, or kidney conditions. Blood tests can screen for most of these.
Common culprits include some antidepressants (mirtazapine, amitriptyline), antipsychotics, corticosteroids, insulin, sulfonylureas, beta-blockers, and some contraceptives.
Yes, if weight gain is genuinely unexplained. A basic panel should include thyroid function (TSH), fasting glucose and HbA1c, cortisol, and a full blood count. PCOS testing may be appropriate for women.
If your symptoms are keeping you from work or study, you can request a medical certificate through InstantMed. A doctor will review your symptoms and issue a certificate if clinically appropriate — typically for 1 to 3 days depending on severity. You don't need to be dramatically unwell; feeling genuinely too rough to function is reason enough.
Yes. Australian-registered doctors can assess your symptoms and issue valid medical certificates via telehealth. You fill in a detailed health questionnaire, a doctor reviews it, and if appropriate, your certificate is delivered digitally. No waiting room required.
You complete a structured health questionnaire covering your symptoms, duration, severity, and relevant medical history. The reviewing doctor uses this information — the same clinical reasoning they'd apply in a face-to-face consult — to determine whether a certificate, advice, or referral is appropriate.
A medical certificate covers the period stated on the document. If your symptoms worsen or don't improve as expected, you should see a GP in person or visit your nearest emergency department if it's urgent. Your certificate doesn't replace ongoing care — it's a point-in-time clinical assessment.
In some cases, yes. If a doctor reviewing your request determines that a common, non-restricted treatment is appropriate, they may issue a prescription as part of a consultation. Not all symptoms require or qualify for a prescription — the doctor will advise you on next steps.
Medical certificates are typically issued in under 30 minutes, available 24/7. Other requests are reviewed within 1–2 hours during operating hours (8am–10pm AEST, 7 days). You'll receive an email notification once your request has been reviewed.
If your symptoms suggest something that requires a physical examination, diagnostic tests, or specialist referral, the doctor will let you know and recommend appropriate next steps. Your safety is the priority — telehealth is a great option for many things, but it's not a replacement for hands-on assessment when that's what's needed.
No Medicare card is required for medical certificates. If you're requesting a prescription or consultation, a valid Medicare card is needed. Our service is private and does not attract a Medicare rebate, though any prescriptions issued can still attract PBS subsidies at the pharmacy.
Our Australian-registered doctors can assess your symptoms and provide advice, treatment, or medical certificates if needed.
Get assessedThis information is for general educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making decisions about your health. Content on this page has been reviewed by AHPRA-registered Australian doctors but does not replace a personalised medical consultation.