Trouble tolerating sublingual methyl b12?

Hi, I'm 33 and was recently told by my doctor to take a high supplement of b12 after bloodwork showed b12 at 205 and MMA at 0.38.  This is likely due to 20 years of a vegetarian diet and lactose intolerance. Possibly related symptoms before diagnosis:  recurring canker sores, mild lethargy, lack of concentration/foggy thinking/forgetfulness, mild depression, mood swings, intermittent dizziness, etc.  I thought taking B12 was a fairly benign thing, but upon taking a sublingual dose of about 500mcg I developed a headache and extreme sleepiness (to the point of not being to able to do anything but lay down) within 5-10 min, lasting a few hours.  Once the sleepiness wore off, I felt like all energy had been sucked from me, and had misc. muscle or nerve pains and weakness.  My mood also went downhill and I felt like crying at the drop of a hat.  I didn't take any supplement the following day, and began to feel better in all aspects.  The next day I tried a slightly lower dose and the exact same thing happened, and the feeling of muscle weakness/twinges of pain and drained energy hasn't left me since then (I took it on Monday, today is Wednesday).  I felt far better before taking any b12.  

My tests indicate the need for b12, but I can't function when I  feel like this - and it doesn't seem like a healthy response.  Any suggestions as to why this might be occurring, or how to supplement in a different way?  Thank you!

[Renee Radenberg]

Vitamin B12 supplementation is needed with a vegetarian diet and for women calcium supplement is needed, too. Suggest you get an iron profile to determine if it is really a vitamin B12 deficiency or a masked iron deficiency. If you need vitamin B12 after additional tests, then suggest asking your MD for another form of vitamin B12 supplement (shots maybe) that would not give you the side effects you described. Hoped this helped you.