Common conditions that mean you are unable to donate blood include:
Inflammatory bowel disease
Chronic lung disease (except asthma)
Chronic fatigue syndrome
Other important information:
High blood pressure, high cholesterol
You can donate while being treated for high blood pressure or high cholesterol levels. If your medication changes you have to wait at least 4 weeks before donating.
You can donate blood if you have diabetes provided you have no complications caused by diabetes and do not need insulin treatment. If your medication changes you have to wait at least 4 weeks before donating.