Feel tired immediately after I took sublingual b12

Hello everyone,

Sometimes I take b12 (hydroxocobalamin, or methylcobalamin+ adenosylcobalamin) sublingually, I feel tired and sleepy immediately, it’s very obvious, it feels like a second before I take the b12 is full of energy, and after I took it or even when I am taking it, I feel very tired, sleepy, and exhausted. Strangely, not every time will feel this, averagely, I take 5 times per day, and 2 times will have this problem

I tried to drink coconut water and take folate when I am tired, but it doesn’t help

I think I take sufficient cofactors except iron, because the blood test report few months before shows I was quite high in ferritin(239 ug/L) and iron Saturation(60.1%), so I am not taking iron

what are the reasons cause the tiredness? would it be iron? or just something like “wake up symptoms” that what I only could do is just enduring?

edit: beside of tiredness, I also have short of breath and rapid heartbeat