Be sure that you are getting the right type of B-12. I was getting the Cyano type of B-12 for injection and it was very hard on my body. I had to lay down for 2 hours after each injection, so I switched to a double dose of sublingual methyl type of B-12 and things smoothed out.
There are 4 types of B-12: Cyanocobalamin, Hydroxocobalamin, Methylcobalamin and Adenosylcobalamin
From:
www.globalhealingcenter.com/natural-health/four-types-vitamin-b12/ 1. Methylcobalamin
This is the most active form in the human body. It converts homocysteine into methionine, which helps protect the cardiovascular system. Methylcobalamin also offers overall protection to the nervous system. This B12 form can also cross the blood-brain barrierāwithout assistanceāto protect brain cells. It contributes essential methyl groups needed for detoxification and to start the bodyās biochemical reactions.
2. Cyanocobalamin
This synthetic version of vitamin B12 is created in a lab, which makes it the cheapest supplement option. It offers the most stable form of B12, although it does so through the presence of a cyanide molecule. While the amount of cyanide is not dangerous, it does require the body to expend energy to convert and remove it.
3. Hydroxocobalamin
Bacteria naturally creates this form of vitamin B12, making it the main type found in most foods. It easily converts into methylcobalamin in the body. Hydroxocobalamin is commonly used via injection as a treatment for B12 deficiency as well as a treatment for cyanide poisoning.
4. Adenosylcobalamin
The energy formation that occurs during the Citric Acid cycle requires this form of B12. Although naturally occurring, it is the least stable of the four types of B12 outside the human body and does not translate well into a tablet-based supplement. It can be difficult to find this one in supplement form, although some supplements, like Vegansafeā¢, have been able to stabilize it.
www.globalhealingcenter.com/natural-health/whats-absorbable-form-b12/ Methylcobalamin does not require a methyl group from the body for absorption, saving metabolic energy and cellular resources. The body uses methyl groups to stabilize free radicals and remove toxins, so it is crucial that weāre doing all we can to reserve these groups. Methylation also plays a role in protecting the brain. Methyl groups reduce the impact of dietary glutamate, a non-essential protein known to cause neural damage. So, using methylcobalamin allows the body to retain its ever-so-important methyl groups for toxin removal and health support.