We are inviting all blood donors who usually give blood at one of about 10 selected mobile donation sessions. You are eligible to take part in the study if you are:
- aged 18 years or older
- willing to undergo an additional haemoglobin measurement
- willing to provide a small sample of blood for research, even if your haemoglobin levels are slightly below the threshold for donating blood
- willing to complete an online questionnaire at home (and, thus, provide your email address).