Some people may experience weight gain, fatigue, poor energy, body stiffness, and discomfort in their muscles or bones after using Invega Sustenna for an extended period of time. However, as this medication is typically prescribed for serious mental health issues, you shouldn't stop or switch it on your own. Seeing the psychiatrist who prescribed medication and explaining the weight gain, lethargy, difficulty walking, and bone discomfort is the safest course of action. Your doctor may monitor your blood sugar, thyroid, vitamin D, cholesterol, and side effects. If necessary, they may also change the dosage or think about switching to a different medication. Energy can also be gradually increased by stretching, eating a good diet, getting adequate sleep, and abstaining from alcohol and tobacco.