Anytime is the right time to donate blood and help those in need, but there are a variety of reasons as to why a person might not be able to donate.  This page is dedicated to 101 reasons why you can't give blood.  Please note that not all reasons for why you cannot donate are permanent.

You can't donate blood...

1.  If you have had a positive antibody test for HIV (AIDS virus).
2.  If you are not feeling well for any reason.
3.  If you have had cancer.
4.  If you have had a stroke.
5.  If you have  had a blood transfusion within the last 12 months.
6.  If you have had Chagas disease.
7.  If you have ever had myocardial infraction, coronary artery bypass surgery.
8.  If you have had hepatitis any time after your eleventh birthday.
9.  If you have had open-heart surgery within the past three years.
10.  If you have had Tuberculosis (T.B.), you may not give until two years after the completion of treatment.
11.  If you have a cold.
12.  If you have multiple sclerosis.
13.  If you have used narcotic drugs by intravenous route (injection into a vein directly), even once.
14.  If you have had the measles then you must wait until 3 weeks from the day of exposure.
15.  If you are pregnant, you can't donate until six weeks after delivery.
16.  If you have had syphilis in the past 12 months.
17.  If you have taken antibiotics, you can't give until two days after a treatment is over if they are for an infection.
18.  If you have had an abortion or miscarriage then you must wait six weeks if it is in the first trimester (12 weeks).
19.  If you have sniffed cocaine or any other restricted drug in the last 12 months.
20.  If you are a woman who is menstruating know it is safer to donate a week after.
21.  If you have difficulty breathing, shortness of breath, or asthma, know you must have no difficulty breathing on the day of donation.
22.  If you are a commercial sex worker.
23.  If you have had hepatitis in the mast 12 months.
24.  If you have had jaundice in the past 12 months.
25.  If you have had a tattoo in the past 6 months.
26.  If you have had semi-permanent make up or cosmetic treatments that involve skin piercing in the past six months.
27.  If you've received human pituitary extract (a growth hormone/fertility treatment before 1985).
28.  If you have ever had syphilis.
29.  If you weigh less than 110 lbs.
30.  If you are under 17 in most states, unless you are 16 with parental consent if allowed by state law.
31.  If you are male and are shorter than 5'1".
32.  If you are male and weigh less than 130.
32.  If you are female and are shorter than 5'5".
33.  If you are female and weigh less than 150.
34.  If you have low hemoglobin/hematocrit levels.
35.  If you have an acute infection you should not donate.
36.  If you have received immunizations for German Measles (Rubella), MMR (Measles, Mumps & Tubella), Chicken Pox, or Shingles, then you must wait 4 weeks.
37.  If you have received immunizations for Red Measles (Rubeola), Mumps, Polio (by mouth), and Yellow Fever, then wait two weeks.
38.  If you have ever used bovine (beef) insulin made from cattle from the UK, you are not eligible to donate.
39.  If you are on blood thiner.
40.  If you have a blood clotting disorder.
41.  If your blood pressure is above 180 systolic and 100 diastolic, or if your blood pressure is under 80 systolic and 50 diastolic.
42.  If you have Creutzfeldt-Jakob Disease (CJD), or if you have a first-degree blood relative with CJD.
43.  If you have had Malaria then wait 3 years after completing treatment.
44.  If you have sickle cell disease.
45.  If you have had oral surgery in the past 3 days.
46.  If you have had gonorrhea in the past 12 months.
47.  If you have traveled to Iraq in the last 12 months.  This is related to concerns about Leishmanaisis.
48.  If you have hemochromatosis the American Red Cross will not accept you.
49.  If you have a sore throat.
50.  If you have a respiratory infection.
51.  If you have the flu.
52.  If you have already donated whole blood within the last 8 weeks.
53.  If you have had a heart attack in the last 6 months.
54.  If you have had a bypass surgery in the last 6 months.
55.  If you have had angioplasty in the last 6 months.
56.  If you have had an episode of angina in the last 6 months.
57.  If you have a pacemaker, you may not donate if your pulse is below 50 beats per minute, or above 100.  You must also have a small number of irregular beats and you must meet the other heart disease criteria.
58.  If you have suffered from symptoms of a heart murmur in the last 6 months.
59.  If you are not given the immunization for exposure to hepatitis B, wait 21 days after immunization.
60.  If you have received a smallpox vaccination, you are asked to wait 8 weeks (56 days).
61.  If, from January 1, 1980 through December 31, 1996, you spent (visited or lived) a cumulative time of 3 months or more in the United Kingdom.
62.  If, from January 1, 1980, to present, you had a blood transfusion in any country in the United Kingdom.
63.  If you were born in or lived in Cameroon, Central African Republic, Chad, Congo, Equatorial Guinea, Gabon, Niger, & Nigeria since 1977, you are not eligible.
64.  If you have traveled in an area where Malaria is found, you're asked to wait 12 months.
65.  If you have spent a long period of time in countries where "mad cow disease" is found, you are not eligible.
66.  If you have the mumps, then you must wait until three weeks from the day of exposure.
67.  If you have the chicken pox, then you must wait until three weeks from the day of exposure.
68.  If you have Addison's Disease, you should not give blood.
69.  If you have Adrenal Disorder, you should not give blood.
70.  If you have a sinus infection, you should not give blood.
71.  If you are on steroids, you should not give blood.
72.  If you are on immunosuppressive drugs, you should not give blood.
73.  If you have Rheumatoid Arthritis, you should not give blood.
74.  If you have Lupus, you should not give drugs.
75.  If you hare a hemophilia, you can't give blood.
76.  If you have taken Tegison for psoriasis, you can't give blood.
77.  If you have received any type of organ transplant from another person, you can't give blood for 12 months.
78.  If you are male and have had sex with another male, you can't donate blood.