This is a question that probably hasn't occurred to many people, but is worthy of consideration. Donated blood saves countless lives each year, and there are over 370 million diabetics worldwide. If we are to maintain the stock of blood necessary to treat patients, those with diabetes may be required to donate.
Usually blood donors are required to be healthy people who are not carrying any infections, whether bacterial, viral, parasitic or fungal. This ensures their donation is seen as low risk, to themselves and to the receivers. This is not the case with donations from someone who has diabetes. If a diabetic donates blood, there is a risk they could become hypoglycemic (experience low blood sugar) shortly afterwards. Hypoglycemia occurs when the blood sugar levels in the body drop below a safe point. Immediate attention and treatment is required so that the blood glucose can be restored to a safe level.
Although some may regard it as unfair, those with type 1 diabetes are often prevented from donating blood for sound reasons, namely the negative impact it could have on both their health and that of the recipient. This is partly because those with this type of diabetes regularly use insulin treatment, which can have a lasting effect on the antibodies produced in their blood. For this reason it is not recommended that their blood is transferred to someone else, as this could cause an adverse reaction.
It is also possible that the blood of a type 1 diabetic will contain fewer platelets than that of someone without the condition. This, in effect, means that more blood would need to be donated in order for the quota to be met.
On the other hand, those with type 2 diabetes will generally not face the same exclusion. If their condition is properly managed through exercise and suitable medication then, depending on their overall health, they may be eligible to donate blood.
Anyone with type 2 diabetes shouldn't be disheartened if they are told they cannot currently donate blood. Often, once the condition is under good control and as long as they have no clotting, heart or kidney complications, they may be allowed to donate in future.