Recently, there has been a genuine shortage of blood, platelets, and plasma ever since the COVID-19 pandemic. This has caused people to have to delay life-saving emergencies. This is a genuine shortage where people's lives are being affected by said shortage. Therefore, I believe it is a moral obligation to donate blood, platelets, and plasma as much as allowed by the donation center. By doing this, you are saving lives and it is pretty inexpensive and cost-effective.
Sources:
https://www.redcross.org/about-us/news-and-events/press-release/2024/red-cross-declares-emergency-blood-shortage-calls-for-donations-during-national-blood-donor-month.html
Furthermore, I talked to a person who took my blood. Can't provide a source on that, but I am guessing the person who took my blood wouldn't lie just like that.
Doing good Better has some estimates on the effect of individual consumption choices on animal production, and takes them to be positive. I think its widely believed that they matter - raising animals costs money, and if corporations sell less animal products, they will produce less animals.
I have no especially interesting answers to the healthcare question.
Both actions will be much less effective than e.g. developing a regular donation habit, getting a good degree and choosing a world-improving career etc. But I don't think its healthy (or common!) for EAs to focus only on the most life-saving choices in their lives. Many EAs are vegan because they (rightly!) think it is just wrong for animals to be held in horrible conditions. Many EAs donate blood because they (probably rightly) think its an easy and positive way to help someone. I think its a good practice to not only focus on the highest-impact choices, but also to aim for a lifestyle in which we can integrate some lower-effort prosocial habits that one believes holds moral value.