First of all, the conditions suitable for blood donation, in fact, if you can meet the blood donation form, doctor's physical examination and blood test, you can say that it is suitable for blood donation. If you are in poor health, the doctor will definitely not let you donate. He is more nervous than you.
Besides, there are many reasons for your poor health. If it is self-feeling, I suggest you try again when you feel better, and you can have a free physical examination by the way. If you have other diagnosed symptoms, such as anemia, it is recommended not to donate blood, and you can't donate blood after you go.