Here are general guidelines for who can donate blood, courtesy of the University of California San Francisco Medical Center:

• You must be at least 17 years old and weigh at least 110 pounds.
  
  
• You shouldn't have a blood pressure reading of higher than 180/100 at the time of donation. You can still donate if you take one or more blood pressure medications.
  
  
• You shouldn't have a body piercing (excluding ear piercing) or a tattoo applied in the prior 12 months.
  
  
• If you are diabetic, your symptoms must be well-controlled.
  
  
• You shouldn't donate if you have used intravenous drugs, are taking antibiotics for an active respiratory infection, are sick with a cold or the flu, have recently traveled to certain countries that harbor blood-borne conditions, have had hepatitis, or are at a high risk for HIV/AIDS.