The American Society for Metabolic and Bariatric Surgery recommends all gastric bypass patients take a B12 supplement. They recommend 350 to 500 mcg daily as a sublingual (a tablet that dissolves under the tongue) or injections of 1000 mcg once a month. There is also a prescription nasal spray available, which is typically used once a week. Some patients find they need more B12 than that, though; in order to keep my level good, as measured by my labs, I take 1000 mcg injections once a week.
The reason we need to use a sublingual, nasal spray, or shots is because after gastric bypass surgery, we don’t have much intrinsic factor in our pouches and intrinsic factor is needed to absorb B12 from food or from a vitamin supplement that we swallow.
Most people will absorb B12 equally well from a sublingual, from the nasal spray, and from injections. It’s mostly a matter of personal preference. I choose to use injections because I disliked the taste of the sublinguals I tried and because I find it convenient to only have to take B12 once a week. The injections are also very affordable for me because my insurance covers the B12 (I have a very small co-pay) and even though my insurance will not cover the syringes, they are not expensive.
You can visit your doctor’s office to receive B12 injections, but many people choose to administer them to themselves at home. You need a prescription from a doctor to get the B12, which you can fill at any pharmacy.
B12 can be injected intramuscularly, or IM, which means into the muscle, or subcutaneously, or sub-q, which means under the skin. Some medical professionals think it’s absorbed better if it’s injected IM, while others think it’s absorbed equally well if it’s injected sub-q. After discussing it with my primary care physician, I opted to do my injections sub-q because that allows me to use a smaller needle and causes less discomfort. In fact, most of the time I barely even feel the needle break my skin!
It’s not hard to give yourself a B12 shot. You don’t need any special medical training to do it. Your doctor can show you how. If you’re squeamish about sticking yourself (I was for a while, but I finally got up the nerve to try it and discovered it wasn’t so hard after all), a friend or family member can do it for you, if you prefer not to have to visit your doctor every time you need a shot.