You only have energy when you take the phentermine because your body is used to the
dosage that you ingest. When the
phentermine is wering off, your body feels that it needs more of it, and you feel sluggish, and out of energy. it's common for your body to become tolerant to medications. You must talk with your doctor about this also, as it's very important. no energy can be a very negative for your overall quality of life just like the pain is.