Dear Friend, For the symptom you have described there can be several reasons. The most common can be low haemoglobin, low Vit D3, diabetes, or stress. I suggest you get these tests done and see a doctor. Doing physical exercise in morning will keep you energetic in the day, so evening tiredness will reduce. Aslo doing Vajrasana and sarnvangasana after coming back from office will reduce your tiredness. You can check demonstration videos of these Asanas on you tube. Please do not eat any thing heavy before doing these asanas. I wish you a speedy recovery.