Doxycycline does not typically make you tired as a direct side effect. Feeling tired or fatigued while taking doxycycline is more likely due to the underlying infection it is treating, or from other side effects such as nausea, vomiting, diarrhea, or sunburn caused by increased sensitivity to sunlight. These side effects can lead to dehydration or reduced nutrient absorption, which might cause tiredness. If fatigue is severe, persistent, or comes with other worrying symptoms, it is important to consult a healthcare provider. Generally, tiredness from doxycycline or the infection should improve as treatment progresses or after completing the medication.