Thanks! The fact that his B12 levels are low, even though folate is fine, is an indication of SIBO. If I remember correctly Keefer's folate was okay too, but his B12 was low. It's possible it was the other way around though, it was a long time ago. I do remember that one was okay but the other wasn't.
SIBO can be either chronic - generally with no known cause, or acute - secondary to something else. I believe Keefer's was due to the giardia that he was diagnosed with at the same time. Since the original test was negative (the giardia antigen test is what picked it up), he had it for awhile and that probably caused an upset in his digestive system that threw it out of balance.
I don't know that for sure, but once he was treated for the giardia and SIBO he was fine, and never had a recurrence. Some SIBO dogs need long term meds and/or special food for life to keep it under control. The only way we could get formed stool during treatment was to put him on prescription Z/D Ultra (yeah, I know - yuck!), but I was able to transition him back to his regular food following treatment.
How old is Rebel, and how long has this been going on? Did your vet talk about antibiotics too? Generally, it's 4 weeks of either Tylan or Tetracycline.