Comment by sarchertech

The first paragraph is

“ If you visited the rural areas of the states - Chiapas, Chihuahua, Durango, Sinaloa districts, Quintana Roo, you need to wait for 4 months after your return to the UK before giving blood. ”

The US rules also aren’t 4 years (not sure why someone told the OP that). It’s 3 years after undergoing malaria treatment. And 3 months after visiting a malaria prone area.

https://www.redcrossblood.org/faq.html#eligibility-travel