This is all over the net, but it can’t hurt to spread it some more. The following symptoms should always prompt medical attention:

• If you have unexplained weight loss and/or loss of appetite, you may have a serious underlying medical illness.
• Slurred speech, paralysis, weakness, tingling, burning pains, numbness, and confusion are signs of a stroke, and you should get to an appropriate emergency center immediately. Early treatment may prevent permanent damage to the brain or even save your life.
• Black, tarry stools may indicate a hemorrhage from an ulcer of the stomach or the intestine. It is important to stop the bleeding and to rule out cancer as a cause.
• A headache accompanied by a stiff neck and fever is an indicator of a serious infection called meningitis.
• A sudden, agonizing headache, more severe than any you have felt before, could mean you are bleeding in the brain. Go to an emergency room immediately.
• For women: Vaginal bleeding after menopause is a warning sign of possible cancer.
• For men: A lump in your testicle with or without a small lump in the groin could be serious. Testicular cancer is more commonly found in testicles that did not naturally descend from the abdomen to the scrotum.

My only query is some kind of timescale on the appetite - sometimes I just don’t feel hungry, how long should that go on before I start to worry?

Via Lifehacker Health-Hack, via WebMD.