I doubt the B-12 disagrees with you. The dehydration you mentioned has nothing to do with water soluble vitamins. You are dehydrated because you are not drinking enough water. A head injury can change how things taste and alter appetites. You are likely doing something different with your diet.

There are many different versions of B-12. Get the methyl version in sublingual lozenges. Chew it and let it soak into your mouth.

You have been overly dependent on the doctors and others who have told you to keep working. As you say, your gut tells you to not work until you are recovered. You should trust your gut. The doctors do not have a clue what is going on at your job.

Take time off. Get some quiet rest. That means limited stimulation. Do light activities that do not require cognitive focus.

I don't understand why you have curtailed your non-work activities but are still plowing ahead at work and feeling lousy when you do. If you had made the same choices about work, you would be weeks ahead in your recovery.

Stop the work, not the B-12.

My best to you.

Thanks for the reply.
How much time would you say is reasonable to take off from work? I know it's subjective and everyone is different, a best guess is what I'm looking for. Since the majority of my problems are brought on by working it may be difficult to know at home resting that things are better and it's ok to go back.

On the B12 issue, you may be right but I suspect otherwise. This is very convincingly a cause and effect situation.
And why would I take 1000mcg of b12 if I'm already getting 300% from my regular vitamin and data MrsD provided showing that the body will only absorb 13 of the 1000mcg and expel the rest. I'm already getting 18mcg from the vitamin plus some from diet.
And my eating habits have not changed and I have been drinking plenty of water.

The RDA (recommended daily allowance) is worthless. It has more to do with avoiding malnutrition than promoting good health. If you choose to allow Big Pharma and government institutions control how you think about vitamins, you are on your own. I will not argue against the false data promoted by government health organizations.

300% is pure poppy cock. You are struggling and choose to ignore the best treatments. There are no set standards for time off work. You need time off until you heal. You need B-12 and the others for weeks to let the slow healing take place. If you choose to let your anxieties limit your choices, you alone will suffer.

B-12 did not cause your dehydration. Enough said.

My best to you.