Doctors Note Logo

Published on: 8/18/2026

What health issues could lead to quick excessive weight gain?

Yoshinori Abe

Reviewed by Yoshinori Abe, MD

Internal Medicine

Rapid weight gain is often linked to medical treatments and medications. Common causes include therapies for hyperthyroidism, which can slow metabolism as thyroid levels normalize, and certain prescription drugs like tricyclic antidepressants, corticosteroids, and some diabetes medications. Hormonal shifts triggered by these treatments may lead to fluid retention or increased appetite.

If you've noticed sudden weight gain, understanding the underlying cause is the critical first step toward addressing it. Rather than guessing, take a free, instant, online symptom check to receive personalized insights based on your specific situation. It takes just a few minutes, requires no sign-up, and can help you identify possible causes and decide whether to consult a healthcare provider—empowering you to take confident next steps.

Reviewed for medical accuracy: 07/20/2026

answer background

What brings you in today?

Can I treat this myselfDo I need to see a doctorWhere should I go for careI'm concerned about a symptomConcerned about a possible conditionMy symptoms are getting worseSeeking a second opinion

Not seeing your question? No worries.

Submit your own Question

Explanation

There are a few health issues that can lead to quick weight gain. One of these is the treatment of hyperthyroidism. After treating hyperthyroidism, people might gain weight quickly because their metabolism slows down.

Another reason for gaining weight quickly can be unexplained, like in some cases where doctors are not sure why it happens.

Some medicines can also make people gain weight fast. For example, tricyclic antidepressants, which are used to treat depression, can cause weight gain as a side effect.

If you're experiencing unexplained weight changes or other concerning symptoms, you can check what might be causing them with Ubie's free AI symptom checker to better understand your condition and next steps.

(References)

  • Kyriacou A, Kyriacou A, Makris KC, Syed AA, & Perros P. (2019). Weight gain following treatment of hyperthyroidism-A .... Clinical obesity, 31267667.

  • Harsch IA, & Hahn EG. (2010). [Unexplained weight gain in a 41-year-old woman]. Der Internist, 19902156.

  • Berken GH, Weinstein DO, & Stern WC. (1984). Weight gain. A side-effect of tricyclic antidepressants. Journal of affective disorders, 6238068.

Thinking about asking ChatGPT?Ask me instead

Tell your friends about us.

We would love to help them too.

smily Shiba-inu looking

For First Time Users

What is Ubie’s Doctor’s Note?

We provide a database of explanations from real doctors on a range of medical topics. Get started by exploring our library of questions and topics you want to learn more about.

Was this page helpful?

Purpose and positioning of servicesUbie Doctor's Note is a service for informational purposes. The provision of information by physicians, medical professionals, etc. is not a medical treatment. If medical treatment is required, please consult your doctor or medical institution. We strive to provide reliable and accurate information, but we do not guarantee the completeness of the content. If you find any errors in the information, please contact us.