Why am I always tired? 22 medical reasons for feeling tired

Underactive thyroid

The thyroid is a gland in your neck which is responsible for your metabolism. This is the speed at which you convert food and liquid into energy for the body.If it’s underactive, then your metabolism will be considerably slower. The result of this is that you may feel tired, along with other possible effects such as weight gain.You can have this tested by a doctor and, like diabetes, it can be managed with medication.