I just started taking vit D3 1000 IU and b12 1000 mcg a few days ago and tonight after dinner I started having very bad bloating, stomach cramps, nausea. Are those side effects of these vitamins ? Should I stop , or it will get better in a few days of adjusting to them ? I feel very bad right now.

Are you taking the B12 at least 1 hr before food on an empty stomach in the morning or at least 4 hrs after eating? There is a lot of info on B12 in the Peripheral Neuropathy Forum - look for the B12 sticky at the top of the page.
Good luck.

Yes I take it on empty stomach and yes I went trough all the posts. I was hoping somebody can help me .

There has been a very few posters here, who seemed to have trouble with Vit D. That always puzzled me, since the Vit D is such a tiny amount in the tablets or caps.

The RX version of D is a big liquigel and does have sorbitol in it, which "might" affect some people as a laxative. But even that (50,000 IU D2) is a stretch.

We are back to --- stop both and wait a week, and begin the B12, alone for a week and see what develops. If nothing happens, then add back in the D. The D does not have to be on an empty stomach, only the B12 needs that special circumstance.

So do you think the vit D could be actually giving me a problem ? I thought to stop the vit D and see how I react then. I take b12 early in the morning on empty stomach and take vit D in the afternoon with food. The cramps last night were like I never had in my life, started in lower abdomen right after eating dinner, and later it was lower and upper abdomen, lasted for a few hours ( not very bad in the beginning ) then it went away, I even had a banana before going to bed. 4 years ago I started taking vit D3 5000 IU but it was giving me constipation so I stopped ( and never did try again taking it until now, that's why this time I started with 1000 IU ).

There are so many viruses out there now affecting the GI tract.

And food borne illness is common.

I did a 3 week long Candida cleanse (NOW brand) and once the Candida died... boy was I sick for a week. I stopped it and recovered, and now I am a "new person"... Candida causes lots of gas/bloating etc.

If you are taking Nexium or any other acid lowering drug, you will ferment protein in the bowel and also get really sick. The acid in the stomach is needed to break up protein you eat into smaller bits, so the enzymes from the pancreas can digest it.
Without acid... the bacteria ferment the protein into GAS and diarrhea. Too much gas= severe cramping as well.

Our processed foods now contain many gums as thickeners, and also now, propylene glycol.. These ferment in the bowel as well ... reading labels can help avoid these new irritants.

I'm not taking anything, birth control pills only. And I actually found out on this site that bcp can deplete the body of b12 , none of my dr.s ever mentioned that to me, and I take bcp for 15 years ! Last night I tried the drug interactions site, and there said no interactions between vit D3, b12 and my bcp, but on mayoclinic site they are saying that b12 and bcp can interact ! so what's the truth about that ? because for a moment last night I thought the interactions is a problem.

Web sites often list interactions in a general way.

There are two types of interaction.
1) One is where one drug depletes another (as with your bcp)
2) The other is where one drug increases the amounts of another drug--- as in some liver enzyme blocking actions. This type is a true interaction, but different than #1.

It is not really an interaction which you have from the bc's. It is a side effect of those hormones on the body, with reduces the B-complex metabolism(including B12). An interaction in the purest sense would be B12 conflicting with bc's, as in reducing the bc concentration in the blood leading to failure of the bc's to prevent a pregnancy. But this is not what the "interaction" is in reality, which is the negative effect bc's have on B12's ability to work in the body properly.

Thanks MrsD - if bcp's can have this effect on B12 metabolism could HRT do the same?

Yes, the hormones do it regardless of the reason you are taking them.