Viagra - I take 50mg pills but dont seem to b working can I double up taking two pills to equal?

Yes. 50mg is recommended to start. It works for 70% of men. If it doesn't work for you, yes, try 100mg which is max for 24 hours; it works for 80% of men, but side effects can be greater.
Ask for prescription of 100mg as it costs the same as 50mg, then pill cut 1/2 for. My doctor prescribes 100mg with instructions to take 1/2 or 1 pill as needed. For some, 25mg works so they are lucky to buy 100mg and pill cut 4 quarters for 4 uses.
If 100mg also doesn't work (need to try it a few times), then try Cialas or Levitra as some users report that they tried all 3 and found one or 2 don't work for them.

You also need to know how this medicine works -- the pill only works if you are aroused, and produce nitric oxide setting off other chemicals. Viagra keeps the body from breaking down the chemicals that produce the erection and keep the erection. If you can't get an erection, Viagra and other pills won't do anything (they only help to maintain the erection, but can't make it).

Everyone is different, this is a question for your Dr as this stuff has other effects on the body, please consult the physician who know your personally before modifying any instructions on a prescription. Hope this helps.

Not without the dr ordering it. Give him a call first.