Well, at this point it may be a risk/benefit analysis on both arms, if the veins in her left arm are beginning to collapse after 3 treatments. How many more does she have? Why does being diabetic prevent her from getting a port? I would think that would still be the best route to go, especially being diabetic, if she still need more infustions, tests, bloodwork etc. It would definitely spare her veins from the trauma, and cause less bruising.

How many treatments are planned for her? I second NJ - the port really does help a ton. It's weird... but worth it.

I'm so sorry your mom is struggling so. I read a bit on your profile, and it sounds like chemo has been rough on her. Her health care team should be able to help make it better with meds and perhaps with dropping the amount of chemo drugs.

Good luck. This is a hard time.

Getting infusions on the arm where lymph nodes have been removed can trigger lymphodema. I agree with the other posters that she should consider a port, unless there's a medical reason not to.