Don't know about alternating, but I have learned by experimenting that Fred and Rich are both right, at least in my case. I tried all four forms. Cyano was the weakest, it helped a little but not enough to take regularly. But I take the other three forms daily, and that makes a huge difference, I need all three of the natural forms. Tried the ProHealth B12 Extreme combo tablet, but I can not set the dosages that way. The dose/ratio that works for me, and has been working for several months now, after I worked up gradually, is: 5,000mcg mB12, 1500mcg aB12, and 1250mcg hB12. Some days I take more mB12, but do not take more than 10,000mcg total B12. And this is probably effective because I am using the more effective brands Fred recommended for mB12 (Jarrow) and aB12 (Country Life), plus hB12 as Rich recommends, but for that I am using ProHealth's hB12 (their hydroxy B12 works well and is less expensive than the other brand). Since the aB12 has folic acid, I take that in the PM, several hours apart from methylfolate. This combination, along with supporting supplements, has restored my ability to work (part-time low-stress work at home, but still, that is a vast improvement). If I stop taking the B12, I only last about 12-24 hours before major symptoms start returning.
Could you post a link to the hb-12 on Prohealth ? I can't seem to locate it on my own.
Never mind, I found it. It's the sublingual tabs, right ? It helps when I spell things correctly.