Extreme fatigue- B complex vitamin

Since starting my health and fitness journey, I've been eating a mostly vegan diet (vegan until dinner every day, vegan dinner 3-4 times per week). I've been a vegetarian for years and I'm lactose intolerant, so this diet isn't a giant change for me. However, I decided to start taking a B complex vitamin supplement to prevent any deficiencies from developing. I took the first dose last night (Whole Foods brand vegetarian formula, in case it matters) and then slept horribly. I haven't had caffeine for several years and ever since I gave it up, my sleep schedule has been like clockwork. It's rare for me not to sleep through my 8 hours peacefully and wake up feeling refreshed and energized. Today I am extremely fatigued- more than I would expect even considering my bad night of sleep. I feel like I could fall asleep at my computer at work in the middle of a busy office! I've never felt so tired in the middle of the day. I know some of the B vitamins can boost energy and I'm wondering if anyone has experienced anything like this after taking a supplement at night. Maybe my energy was revved up all night and I got even less sleep than I thought. Obviously, I'm going to start taking the vitamin in the morning and discontinue using it if these symptoms persist, but I just thought I'd see if anyone else has had similar side effects. Of course, it's always possible that I'm coming down with something and it has nothing to do with the B vitamins at all.

A small minority of people cannot take B vitamins -- they have atypical reactions to the B complex. Some have allergic responses (usually B3 and B6). Others have neurological responses (migraine, headache, fatigue, irritability) and usually to any of the B vitamins.

So, it is possible you cannot tolerate either one of the B vitamins or perhaps more than one.

That you experienced fatigue is atypical and should have nothing to do with when you take the dose. Best of luck.

Last year I too, was really feeling dragged down and tired so I had my blood checked and it turned out I was dangerously anemic (which is a distinct possibility for vegetarians as well).  If this problem persists you ought to have your blood checked.  Good luck.

If the problem happens again and, if stopping taking the vitamin doesn't correct it, then see your doctor.  Any serious swings in behaviour or energy levels are worth checking out if there's no obvious cause.  I'd agree with edelhaus that anaemia is always a possibility.

I encourage you to go to the doc for a physical and bloodwork. Yes B vitamins can give you energy but there may be an underlying issue like iron,blood sugar,b12. I have a condition which many who have it have very low b12 that it cause neruo issues. I am not saying this is you cause most have pain,tingling etc but it is not good to self treat.