When your skin turns red at the beach, you know that's your body's way of saying you've had too much sun! Unfortunately, some other body "warnings" aren't that obvious. So here's a list of surprising warning signs, and what they could be saying about your health, according to our friend Dr. Mehmet Oz: * Warning sign #1: You have yellow fingernails. Dr. Oz says that could mean you have diabetes. When some people have high blood sugar, the excess glucose in their system attaches to collagen proteins, which can turn your skin and nails yellow. So, if your discolored nails are accompanied by lots of extra trips to the bathroom, see your doctor about a diabetes test. * Body warning sign #2: You have short, thinning eyebrows. That could mean you have a thyroid disorder. Dr. Oz says one of the jobs of your thyroid is to regulate how quickly body cells replenish themselves - including the ones in your hair follicles. So weakening eyebrows are often one of the first red flags that your thyroid hormone levels are out of whack! Fortunately, a simple blood test from your doctor can usually determine if you have a problem. * Also watch out if your ring finger is longer than your index finger. That could mean you're at a higher risk of osteoarthritis, which is a condition involving weakening joints. A study in the journal Arthritis & Rheumatism found that people whose ring fingers are longer than their index fingers are twice as likely to suffer from the condition, and the risk is even higher if you're overweight! The good news is that you can reduce your risk of osteoarthritis significantly by losing just 5% of your body weight. * One more surprising body warning sign: You get frequent heartburn. Dr. Oz says chronic indigestion could actually raise your risk of esophageal cancer! That's because heartburn involves stomach acid creeping up into your throat, and over time, that can damage tissue until it becomes cancerous. So, talk to your doctor if you have persistent heartburn, and get a thorough throat exam at least once a year.