self injecting vitamin b12 Injection Sites: All You Need to Know Safe B12 Injection Guide at

[9] [5] It is given by mouth, by injection into a muscle, or as a nasal spray

Never discontinue prescribed B12 treatment without medical supervision, particularly if you have pernicious anaemia or neurological symptoms of deficiency

Concentrations of 10-20mg/ml work well, requiring 0.05-0.3ml injection volumes that standard insulin syringes measure accurately

That is a very specific use case, but it tells us something important

A 2017 meta-analysis of data from 15 trials, including more than 71,000 participants at risk of or with existing CVD, showed that B-vitamin supplementation had no significant effect on risk of myocardial infarction (heart attack) or all-cause mortality but reduced risk of stroke by 10% (RR, 0.90

B 12 deficiency can also adversely affect the methylation reaction, increasing inflammatory responses [38], and reducing CD8+ and natural killer cell activity [39]