Sorbitol,Stevia,(and likely mannitol) and xylitol are known to worsen some autoimmune conditions by altering the gut in the wrong way[Early Post, Stevia Post,Another Post]. Frequently they are incorrectly listed as “inactive”. While B-12 supplementation is needed/recommended for many autoimmune conditions, the indigestion of these additives with such conditions have not be tested and there is evidence suggesting significant risk. A related post elsewhere
These additives may be why B-12 injections work better than supplements — because these additives contribute to gut bacteria dysfunction.
So, which B12’s are not safe from this perspective? Well, the following are IMHO, not safe.
- Swanson Ultra Methylcobalamin (B-12)
- First listed ingrediant: Sorbitol!
- Swanson Ultra Supplemelts Sublingual Vitamin B-12
- Jarrow Formulas Methylcobalamin (Methyl B12)
- Now Foods B-12 , Methyl B-12
- Sorbitol (#3 ingredient
- Vitamin B-12 Complex Liquid
- B12 Liquid 1000mcg 30ml/1oz by Pure Encapsulations
- Kirkman Labs, Methylcobalamin Concentrated Powder
- Mannitol, Sorbitol
The following appears to be safe:
- Methylcobalamin 1000mcg 60ct by Pure Encapsulations (Note: mystery plant material)
- BulkSupplements Pure Vitamin B12 1% (Cyanocobalamin) Powder
Literature on Gut Alternations
- Dietary supplementation with sorbitol results in selective enrichment of lactobacilli in rat intestine. 
- This results in E.Coli (low or none in CFS) being further reduced.
- Xylitol affects the intestinal microbiota and metabolism of daidzein in adult male mice. 
- “xylitol feeding caused a clear shift in the rodent faecal microbial population from Gram-negative to Gram-positive bacteria. In human volunteers a similar shift was observed even after a single 30-g oral dose of xylitol.” 
- “While sugar alcohols …are also notorious for causing digestive distress. Because sugar alcohols are FODMAPs and are largely indigestible, they can cause diarrhea by pulling excess water into the large intestine. The fermentation of sugar alcohols by gut bacteria can also cause gas and bloating, and sugar alcohols may decrease fat absorption from other foods. (14, 15)…Animal studies have found that xylitol causes a shift from gram-negative to gram-positive bacteria, with fewer Bacteroides and increased levels of Bifidobacteria. (19, 20) A similar shift has been observed in humans, even after a single dose of xylitol. (21) “
- “Colonisation with Escherichia coli, Klebsiella pneumoniae, and Streptococcus viridanssignificantly increased lumen to blood clearance of mannitol. Colonisation with Lactobacillus brevis had the opposite effect and reduced permeability to mannitol.” 
- “These results demonstrate that more than 95% of mannitol administered orally is utilized via fermentation by intestinal microbes.”
Bottom Line: We need properly done studies on whether the above sugars have a net positive or negative impact on people with gut bacteria dysfunction/autoimmune conditions.