"I had been taking Shelcal XT for about 2.5 years. In my recent blood test, my Vitamin B12 level was high at around 2000. Shelcal XT contains: Elemental Calcium – 500 mg Vitamin D3 – 2000 IU Methylcobalamin (Vitamin B12) – 1500 mcg L-Methylfolate Calcium – 1 mg Pyridoxal-5-Phosphate – 20 mg Since it contains Methylcobalamin 1500 mcg, I think my B12 may have become high because I took it for a long time. So my doctor advised me to switch to plain Shelcal 500 and Ultra D3 2000 IU. I stopped Shelcal XT and for the past 3 days I have been taking only Shelcal 500 and Ultra D3 2000 IU. I was fine all this time, but for the last 3 days I have been feeling mild breathing difficulty and mild palpitations. Is it possible that these symptoms are due to changing the tablets 3 days ago?"