The rules around donating depend on whether you have ever donated before.
You can become a donor as soon as you reach your 17th birthday.
If you are a new donor, you can start giving blood anytime up to and including your 66th birthday.
If you have given blood before, even if it was some time ago, you can donate up until your 70th birthday.
There is no upper age limit for giving blood, after your 70th birthday providing you are in good health, you can continue to give blood as long as you have successfully donated within the last 2 years.