Should I have blood tests if I already donate blood?

Question

3.5 years ago I became a vegetarian, but in the mean time I have never had a blood test to check the iron value, the B12 amount, the vitamin-D amount and so on. Some people are worried that my nutrition might have deficiencies.

Do I really need blood tests, or am I already safe if I donate blood regularly? Is blood donation an alternative to blood tests? If not, what might be important what they check in a blood test, but they do not in a blood donation.

What I read so far is that the iron amount in blood is checked if you donate blood.

Answer 1

Often a quick hemoglobin test is done before giving blood to confirm you're not anemic, a condition would make blood donation less safe for you. It does not necessarily give a precise result -- you won't know if you're slightly or severely anemic, for example.

Other nutrients like vitamins (B12, D, etc.) are not measured at all during blood donation. Screening for some diseases (e.g. HIV) does happen, but this isn't really relevant to your question, and I also don't remember whether they tell the donor or not.

To get a complete overall picture of whether you've got a nutrient deficiency, you would need to get a blood test. A medical professional can help ensure all of the nutrients you are interested in get measured. (Assuming the results are within normal bounds, this test probably would not have to be repeated often.)

Answer 2

Yes. B12 is especially important to have tested.

The deficiency prevalence among infants reached 45%. The deficiency among the children and adolescents ranged from 0 to 33.3%. Deficiency among pregnant women ranged from 17 to 39%, dependent on the trimester. Adults and elderly individuals had a deficiency range of 0-86.5% ... Vegetarians, regardless of the type of vegetarian diet they adhere to, should be screened for vitamin B12 deficiency.

https://www.ncbi.nlm.nih.gov/pubmed/24667752/