Since I know nothing about your lymphoma or chemo, I hope you understand that what I share is based on our experience with SAA and after treatment collateral damage. You may have other issues I'm not aware of or familiar with that need to be taken into consideration.
The elevated B12 and folate can be a result of your body not being able to utilize it leading to falsely elevated blood serum levels. Figuring out why can be a challenge. Blood serum B12 is the least reliable test for b12 in order to identify a true deficiency. A better indication, but again, not conclusive is to have your homocysteine and MMA (methylmalonic acid) levels checked too. If elevated, there's a strong possibility of a B12 deficiency.
Some of the more current thinking is to look for defects or genetic mutations that deal with methylation. MTHFR defects can effect proper utilization of B12 and Folate. If you search MTHFR on this forum using the search tool above it will give about 8 or 10 threads where this is discussed. It's a very complex process and there's not a one size fits all approach to treating it. Sometimes it's just a matter of taking the proper bio-available forms of B12 and folate. Others have to play with tapering what they take and when. You can get tested for the mutations. I would suggest reading about as much as possible to see what resonates.
On another note.....John's testosterone took a big hit. He's now on bio-identical testosterone replacement. Have they checked your hormones? Restoring it can also help with red cell production.
John's done all three approaches. Desferral, Exjade and phlebotomies. The last being the best approach but not possible in your case. Exjade is the easiest to take since it is oral but can have more side effects. Most prefer Exjade to Desferral since Desferral is a slow infusion over 8 hours. If you have a port or hickman, then its not so bad. But if you have to do the sub-Q, it's a real pain. Exjade is harder on the kidneys than deferral. With either drug, you should monitor kidney and liver function as well as your blood counts.
Marlene, wife to John DX w/SAA April 2002, Stable partial remission; Treated with High Dose Cytoxan, Johns Hopkins, June 2002. Final phlebotomy 11/2016. As of January 2017, FE is 233, HGB 11.7, WBC 5.1/ANC 4.0, Plts 146K.