I've been vegetarian for over three years now, and much of that time has been vegan. I've been supplementing the whole time with a good multivitamin, and often with an extra B12 sublingual vitamin. I also sometimes eat fortified foods, such as Clif Bars.
Despite this supplementation, there are times when I still feel deficient in something. I can feel tired, weak, and have a tingly sensation in my tongue and cheeks. This has led me to add some eggs, cheese and yogurt back into my diet which has really helped me feel better. I feel that yogurt especially has helped me survive as a vegetarian, and I think it's because of the higher B12 content.
As much as eating dairy products has helped me feel better, it also tends to give me acne and a bit of sinus congestion. Both of these problems are generally remedied by drinking green tea. Yet green tea, with all of its amazing benefits, can come with an afternoon caffeine crash. So I was searching for a better solution, and finally found a way to buy B12 shots over the counter in Hong Kong (I'm currently living in neighboring Shenzhen).
After buying the injections, I watched some YouTube videos on how to properly take them. It was a fairly painless shot to my thigh, and some small soreness lasted through the night but was gone the next day. I did get a temporary but sharp headache the next day, which may have been either from the injection or some processed and flavored chips I ate the night before.
Overall, the benefits of the B12 injection have so far strongly outweighed the negatives. I feel better emotionally than I have for months, even years. I have much more energy, optimism and overall excitement for life. I've been off dairy and green tea, and haven't really felt the deficiencies that have brought me to eat dairy or eggs yet.
I know that some people would probably attribute everything I just said to placebo effect. For these people, I would encourage them to research the experiences of Mahatmas Gandhi, who switched from a vegetarian diet to a vegan diet, and eventually ended up on a sick bed, too weak and depressed for his usual activities. Drinking milk brought him back to health and strength, and he was never a vegan again. His story and many other similar stories can be viewed here.
In conclusion, I strongly feel that the B12 injection has worked wonders on me. I feel more positive and energetic, and I'm hoping that I can continue taking them with positive results. I love the vegan diet, and so far, this seems like my best chance at being a vegan. That being said, I'm a realist. If I somehow did have a negative reaction to the B12 injections or fell into deficiencies again, I would likely return to eating eggs and yogurt to keep my B12 levels up (preferably two free range eggs a day).