How long does it take to build back up something you are deficient in?

RyRy

Early last week I found out I have low B12 as a side effect from my acid reflux and medicine. It was actually my family doctor that noticed this: my gyno who is currently helping us with our TTC issues never tested for that to my knowledge, or at least never mentioned it being low.

I made sure to pick up some B12 vitamins and have been taking them for a few days now. I got to looking into side effects of low B12 and fertility issues can be one of them.

My fertile week also started a couple days ago as well. If low B12 was part of our fertility issues, would have only taking the vitamins for a few days now so close to my fertile window make much of a difference? Or do I probably need to take it for a month or more before it really helps?