B12 Dangerously Low in 2023, Treated with Injections, and Now Dropping Again

Hi everyone. I'm trying to see if anyone else has experienced something like this and if they were able to ever find out an underlying cause for it.

In 2023, my B12 levels were 159 pg/mL. The person going over my labs with me told me that was considered dangerously low if it was that low for a long period of time due to the potential for neurological symptoms to pop up. My eyesight actually was deteriorating around this time, but my only other noticeable issue was extreme fatigue.

It was treated with monthly injections and retested. It was in the 400s range when retested. I was told to stop injections since they did test me for Pernicious Anemia with negative results. The only thing they could come up with was just deficiency that needed to be treated with those injections and then just keep an eye on it once the levels were reached. Well, the healthcare company sucked and fell through on checking up with me regularly on it.

It is now 2026 and my newer primary care provider decided to check my B12 again since I have been having extreme fatigue. I also struggle with chronic pain now. The B12 is not at an official low, but the provider would like me to restart supplements again because it certainly isn't as high as they would like to see. I will probably be put back on injections.

Has anyone else had this happen? You get your B12 up super high and then it drops again? It's almost like my body is struggling to maintain the levels by itself from food. When my B12 was severely low in 2023, I certainly was eating meals that contained B12. I really have no idea why this happened and now I have no clue why it seems to be dropping again. I'm looking for similar stories to this because I just want to understand what is causing it.

Thanks!