I did serum b12/folic acid and magnesium/calcium tests.

b12 141-750 363
folic acid 12-42.4 14.9
magnesium 0.65-1.05 0.75
calcium 2.14-2.53 2.46

b12 low, should be above 550
folic acid low. I am often taking b complex which has 400mcg of folic acid, but my body do not convert it in active form so I have to take methylfolate
magnesium - not so good, should be around 0.9 but it's "impossible" for me to achieve that because the only forms I absorb is magnesium oil and maybe Epsom Salt (magnesium sulphate) baths.

Calcium - looks OK, but I did take calcium carbonate supplement until few days ago. I should be clear of supplements at least one week before testing so I don't know how relavant is this.

Anyway, I have suspected about b12/folic acid so I ordered supplements few weeks ago so I can start to take it now.