Are you eligible?

Who may donate blood?

Anyone who is in good health, is at least 17 (16 years old with parental consent) years old and weighs at least 110 pounds may donate blood every 56 days.
(1 Pound = 0.45359237 Kilograms)

But here in Medan, they wanted at least 50 kg.

General Eligibility Requirements
Donors must be at least 17 (16 years old with parental consent) years of age
Donors must weigh at least 110 pounds
Donors must present a CBC Donor I.D. Card
Donors must be in good health
Food/Sleep
Eat nourishing meals before and after donation
Drink plenty of fluids before and after donation
Get a good nights sleep prior to donation
Length of Time Between Donations
Whole Blood Collection
Donors must wait 56 days following a whole blood donation before donating again

Reasons for Permanent Deferral from Blood Donation
Hepatitis after age 11
IV Drug User (even one time)
Certain obstructive lung disorders
Certain liver disorders
Persons who have taken Tegison for psoriasis
Persons who have taken human-derived pituitary growth hormone, had a dura mater transplant or who have a relative diagnosed with CJD
Persons with symptoms or laboratory evidence of AIDS or who are considered to have an increased risk for contracting AIDS

Reasons for Temporary Deferral from Blood Donation
Current cold or flu symptoms, including a cough, sore throat and/or fever
Dental work – defer for 24 hours after procedure for root canal, oral surgery, extraction of wisdom teeth; must be asymptomatic in all instances and all packing removed
Pregnancy, miscarriage or abortion – defer for 6 weeks after delivery or termination of pregnancy
Blood Transfusion – defer one year
Malaria – defer for 3 years after last symptoms
Mononucleosis – must be fully recovered
Ear or Body Piercing under non-sterile conditions – one year
Tattoo – unless performed in a licensed parlor either in Ohio or Kentucky, there is a one year deferral

Medications
Most medications taken within 24 hours are acceptable
Antibiotics are not acceptable to take 24 hours before donation
Donors who have taken Accutane, Proscar, or Propecia must be deferred for 30 days after the last dose
Donors who have taken Avodart must be deferred for 6 months after the last dose
Consult with a Nursing Supervisor or Charge Nurse concerning immunizations or injections and the deferral period associated with the immunization
There is no deferral period for the flu vaccine or pneumonia vaccine; there is a three day deferral for the Hepatitis B vaccine; see below for contact information
Diabetes/Blood Pressure
Donors with well-established (not recently diagnosed) diabetes, who are controlled by diet, oral medications and/or insulin therapy, are eligible to donate
Controlling medications must have been used in the 24 hours before donation
Donors with controlled high blood pressure by diet, oral medications are eligible to donate

taken from :
http://www.cbccts.org/donating/index.htm

other reference :
http://www.redcross.org/