Why am I still dizzy after donating blood?

[Mattzechman]

I donated a pint of blood on Friday. That day I felt alright, nothing too crazy. The next day while in formation (I’m in the Army), I felt myself getting real dizzy. To make a long story short, I passed out. Ever since then, I’ve been dizzy every day, getting frequent headaches, and today has been 5 days since I donated blood. I’ve been drinking a heavy amount of water, taking in a large amount of sodium to accompany the water, and eating food with lots of nutrients and iron. A year ago (the last time I donated blood), I also passed out the day after.

To make it more complicated, three weeks ago I started feeling fatigued constantly. When I go to bed and wake up, I have the drowsy feeling like if I took Benadryl, yet I didn’t take anything. I also sleep very heavy, which isn’t normal. At this point, I’m not sure if it’s complicating my blood donation, if there’s an issue I need to get checked out, or whatever. I’m a 20 year old male, in good shape, healthy, etc.

[TheLightSeeker]

It could have to do with lower blood sugar following the blood donation.
Normally you're given a glass of OJ  following the blood draw, to replace the "lost" blood sugar and to help the body process  iron, necessary for  healthy blood cells.
I  suggest you also get your ferritin  levels checked, something that is not checked when you donate blood.  Ferritin is your iron storage.
Best wishes
Niko