. I have low b12 and so have started taking 1 drop of sublingual hydroxycobalamin which is 5mcg.
I know it is a small amount but it has increased my stamina each day. But yesterday I felt awful and today I am worse.
I am worried it is having a negative effect, is this possible?
That is a very small dose. However, conceivably it's possible that it has caused your potassium level to drop, and low potassium can make you feel like crap. Taking B12 and/or folate when you are deficient can cause hypokalemia (low potassium) because suddenly your cells will start dividing more rapidly and doing what they are supposed to do, which uses more potassium, thus causing a deficiency. A simple thing you can try is to drink a couple (or more) glasses of low-sodium V8 or low-sodium vegetable juice, which is high in potassium. Often people will start to feel better within a few hours doing this, if low potassium is the issue.
I recommend low-sodium V8 or vegetable juice because it's low in sugar, and eating a few bananas probably would not give enough potassium.
Symptoms of low potassium can include fatigue (I developed severe fatigue with low potassium), muscle twitches and cramps, cardiac symptoms (palpitations, arrhythmia).
I developed low potassium after starting methylfolate in 2010. I had an initial burst in energy for a couple of days and then severe fatigue. Fortunately I had read Freddd's posts about methylation and potassium and started taking potassium - I titrated up to 1000 mg. a day, in divided doses, over 2 days. It's important not to take a large amount all at once. FWIW, the daily RDA (minimum) of potassium is 4500 mg. I've continued taking 800 - 1000 mg. of potassium gluconate (in 4 divided doses) daily ever since as my body needs it. Interestingly, I discovered I had had symptoms of low potassium off and on even before I started the methylfolate, only never knew what it was.
Also, people with ME/CFS very often are low in intracellular potassium despite normal blood work (which was true for me - my blood work was always in the normal range, albeit on the low side). See
http://forums.phoenixrising.me/inde...ded-in-methylation-treatmt.18670/#post-291422