NHS has said that there is currently a limited amount of data on effective ways of conducting such risk assessments, and that the initial steps of scoping, evidence gathering and testing will potentially take up to two years to complete. Furthermore, NHS Blood and Transplant are in the process of investigating how possible it is for MSM, depending on degree of risk, to donate without even the three-month deferral. In July 2017 however, the UK government reduced the one year deferral window to three months, to take effect in the following months, resulting from SABTO's updated conclusions that "new testing systems were accurate and donors were good at complying with the rules". The UK government advisory committee, SABTO, stated in 2013 that "the risk of transfusion of HIV infected blood would increase if MSM were allowed to donate blood". Proponents of the lifetime restriction defend it because of the asserted risk of false negative test results and because the MSM population in developed countries tends to have a higher prevalence of HIV/AIDS infection. They state the deferrals are based on stereotypes. Many LGBT organizations view the restrictions on donation as based on homophobia and not based on valid medical concern since donations are rigorously tested to rule out donors that are infected with known viruses such as HIV, hepatitis B, and hepatitis C. Meanwhile, for tissues such as corneas, the MSM deferral period is five years in the United States and 12 months in Canada. In Canada, the deferral period for MSM blood donors was decreased to 3 months in June 2019. With regard to blood donation, the United States Food & Drug Administration (FDA) enforces a three-month deferral period for MSM and women who have sex with MSM. They do not otherwise affect other women, including women who have sex with women. The restrictions affect these men and, in some cases, any female sex partners. Restrictions vary from country to country, and in some countries practice of protected sex or periods of abstinence are not considered. Even men who have monogamous relations with their same-sex partner are found ineligible. However, many deferrals are indefinite meaning that donation are not accepted at any point in the future, constituting a de facto ban.
Temporary restrictions are sometimes called "deferrals", since blood donors who are found ineligible may be found eligible at a later date. Many countries have laws, regulations, or recommendations that effectively prohibit donations of blood or tissue for organ and corneal transplants from men who have sex with men (MSM), a classification of males who engage or have engaged in sex with other males, irrespective of their sexual activities with same-sex partners and of whether they identify themselves as bisexual or gay.