That is why blood cannot be donated .

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Blood donation means giving life. Because if there's a lack of blood in the case's body, the only way to save his life is to give him blood incontinently. But you can not contribute blood if you want to. In case of blood donation, one's physical condition is the main consideration. For this, first you have to be between 18 and 60 times of age. Second, the minimal weight should be 45 kg. Thirdly, body temperature, blood pressure and palpitation rate should be at normal situations. Hemoglobin in the blood should be at least 75.
In addition, there are a number of health problems, in any of which you won't be suitable to contribute blood. Including

Cancer;
Heart complaint;
Conditions in bleeding Johnny;
Abnormal weight loss;
Insulin- controlled diabetes;
Hepatitis-B infection;
Crohn's nephritis;
HIV/ AIDS
Liver complaint;
Tuberculosis;
Polycythemia variants;
Asthma;
Epilepsy;
Leprosy;
Schizophrenia;
Rheumatic fever;
Syphilis infection;
Endocrine diseases;
Hepatitis-C.
Now let's find out how long blood can't be bestowed in any case
Blood donation can not be done till 6 months after revocation/ surgery.
Blood donation can not be done till 12 months after recovery from typhoid.
Tattoo mark- Blood donation can not be done for 6 months after getting tattoo.
Blood donation can not be done from 6 to 12 months after birth.
Immunization (cholera, typhoid, diphtheria, tetanus, cut, gammagobulin)- Blood donation can not be done for 15 days.
Blood donation can not be done till 2 weeks after tooth birth.
If you have eczema, blood donation can not be done till you get cured.
If you're addicted to banned medicines, you can contribute blood after complete recovery.
Blood donation can be done after recovery of original infection/ menstrual/ common deep freeze.
Covid-19 infected person can contribute blood 28 days after nimbus negative or complete recovery.
Blood benefactors can contribute blood formerly in 3 to 4 months.