What are the more subtle signs that a dog is in pain?

My dog has been prescribed narcotic pain killers for his pain associated with terminal cancer. He doesn't need the meds around the clock, they're only to be given as needed (which isn't often).I know the obvious signs of pain, but since dogs, unlike us, never learned that showing pain may mean relief, they tend to keep it to themselves.So what are some subtle pain signs?

I'm not sure what signs you know...but you are right. It doesn't stand in good stead for a dog to show its weakness....much like prey animals, they would prefer to give the impression of good health and strength.Panting, salivation, restlessness, vomiting, diarrohoea, tucked in abdomen, vocalising, crying, not eating, not drinking, chewing on paws, constant licking, lethargy, hair loss, localized heat - there are quite a few..your main indicator will come from knowing what behaviour was 'normal' for your dog prior to becoming unwell. All the best

Isolating itself,finding a dark area hid,lip licking,pacing,fear of quick movement avoiding jumping or other activities that cause pain and some dogs become clingy when feeling poorly