• Vitamin B_h: biotin
• Vitamin B_m: “mouse factor”: also used to designate inositol
• Vitamin B_p: choline^{[dubious – discuss]} Choline is only required for survival of some mutants. Most commonly it is synthesized in vivo de novo.^[28] May be added as supplement especially when methionine supply is limited^[why?]

• Vitamin B_t: L-carnitine
• Vitamin B_v: a type of B₆ but not pyridoxine^{[clarification needed]}
• Vitamin B_w: a type of biotin but not d-biotin^{[clarification needed]}
• Vitamin B_x: para-aminobenzoic acid