Depo-Medrol side effect - meaning of dark stools?

I received a 3 month Depo-Medrol shot for breathing problems related to Asthma on Monday afternoon, the 8th of Sept.
The next day had a little relief for breathing..understand it builds over time. Either that night or Wednesday my stomach was upset...belching...noticed stools were very dark brown.  Thought it was from some hot wings I had eaten Tuesday evening although never had a problem before that one Alka Seltzer wouldn't help..  Thursday it was the same...remembered I had put 1/2 scoop of flax on cereal Tuesday morning...since I had never taken that before thought maybe that was the problem.  All this time I am taking Alka Seltzer to feel better...works for awhile but then discomfort comes back.  Late last night I thought this has gone on too long...maybe I should check Depo Medrol (only the second time I have ever taken...first time it worked beautifully for 2 months) although thinking, what could that do to bowels?  Well, first side effect for calling Dr is "dark stools"!   It is now 5 AM Saturday morning...of course the Dr is not in...just finally went again and still dark...am so disappointed!  And a little scared!  I am a bit constipated so was somewhat miserable last evening...had not gone since early yesterday morning.
My question...what is going on here?  Must I go th the ER?  I have never had any major stomach or bowel problems...an occasional Alka Seltzer for indgestion but that is it.  I am a 68 year old female, well most of my life but over weight, until this Asthma thing about a year and a half ago.  I was supposed to have a colonoscopy (5 years) in 2007 but because of constant breathing problems I have put it off.  Am I in trouble here?
I'll wait for your response....
Ann

[Kevin Pho, MD]

I can't give personal recommendations (i.e. whether to go to the ED or not) without personal evaluation.  If there is any doubt, I would go.

Dark stools can be caused by upper GI bleeding - like an ulcer or inflammation.  I would discuss this symptom with your personal physician, and possibly pursue an upper endoscopy.  

If negative, then it is possible that the dark stools may be a medication side effect.

This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.

Kevin, M.D.
www.kevinmd.com