Certain medications may cause weight gain. These act by increasing appetite or by fluid retention.

• Prolonged Oral steroids intake, prescribed for some chronic ailments cause weight gain. These increase appetite and also cause fluid retention.
• Many antidepressants also increase one’s appetite.
• Some antihistamines increase one’s craving for sweets and thus help in weight gain.
• Oral contraceptives
• Drugs prescribed for Hormone Replacement Therapy (HRT)
• Lithium used for manic bipolar disorders
• Breast cancer medicines
• Beta blockers
• Anti-seizure medicines

Not all people using these drugs gain weight. The same drug may cause weight gain for some people and weight loss for other people.