Our bodies have a lot of ways of signaling us that something is wrong. Sometimes it's super obvious: A fever and nausea is likely the flu; congestion and sneezing means you probably picked up that cold that's floating around your office. But then there are more subtle signs—dark undereye circles, slightly discolored fingernails, dry lips—that are easy to miss or write off as no big deal. Keep an eye out for these understated red flags on your body and learn how to distinguish between when it's OK to let it go, watch and wait—or hightail it to your doctor's office.
Your fingernails turn white when you press on them
What it might mean: All nails blanch a bit when you apply pressure, but if yours stay white for up to a minute, you may be anemic and low on iron. "Many women, especially those with heavy periods, can become anemic without even knowing it," says Katherine Johnston, M.D., instructor of medicine at Harvard Medical School in Boston.
Your next step: Have your blood's ferritin levels tested. You may need to eat more iron-rich foods such as salmon and spinach, but don't take an iron supplement without your doc's say-so.
What it might mean: It's either time to chug some water or take a closer look at your vitamin A intake. "I had a young woman who didn't know that she was getting 20,000 international units of vitamin A every day—that's four times the recommended daily value and approaching the toxic dose of 25,000 IU—from two different supplements," says Carolyn Jacob, M.D., a dermatologist in Chicago. In healthy amounts, vitamin A is essential to skin-cell turnover, but too-high levels can sap moisture and, if you're pregnant, cause birth defects. "It completely dried out my patient's lips and skin," Dr. Jacob explains.
Your next step: If you take supplements, check the labels to make certain you're not taking in more than 5,000 IU daily; be sure to account for the vitamin A you get from natural sources such as eggs and fortified milk, too. Soon after you stop overdosing, your pucker should plump up again. And regardless, down plenty of water—especially if you work out. Remember, if you feel thirsty, you're already dehydrated.
What it might mean: Salty snacks and PMS are obvious bloat culprits, but if you shun the shaker, your period isn't due for weeks and still your rings are tight, a sluggish thyroid may be to blame. This condition, called hypothyroidism, occurs when the gland underproduces the thyroid hormones needed to regulate metabolism, heart rate and more, says Rebecca Bahn, M.D., professor of medicine at the Mayo Clinic College of Medicine in Rochester, Minnesota.
Your next step: Don't write off puffiness as inevitable, Dr. Bahn warns. "Untreated hypothyroidism can lead to heart disease, and if you're even slightly hypo and get pregnant, it could affect the baby's brain development." A blood test can reveal if your thyroid isn't producing enough hormones; if so, your M.D. may prescribe synthetic hormone pills, likely for the rest of your life. Once you find the right dose, your metabolism (and fingers) should return to normal.
White patches in corners of your mouth
What it might mean: You've developed a yeast infection. (Nope, it doesn't occur only in your nether regions.) Anything that causes the corners of your mouth to crack—such as a B-vitamin deficiency, which can damage your mouth's mucous membranes, or even drooling during sleep—creates a warm, moist environment where yeast thrives, according to Amy Derick, M.D., a dermatologist in Barrington, Illinois.
Your next step: See your dermatologist or general practitioner, who can prescribe a topical antiyeast medication. In addition, make sure you're getting enough B vitamins in your diet; you find them in whole grains like whole-wheat bread and quinoa and lean proteins like chicken and fish. If the infection keeps coming back, try avoiding white breads and sweets. "Yeast feeds on refined flour and sugar, so cut back on them," says Tara Gidus, R.D., of Orlando, Florida.
What it might mean: If it's chilly out or you are tense, blueberry-hued fingers and toes may signal Raynaud's disease, a condition in which blood vessels in extremities narrow in response to cold or physical stress. This reaction limits blood flow to those areas, causing skin to turn blue and feel cold.
Your next step: Your physician can diagnose Raynaud's based on your symptoms alone. If it is Raynaud's, the best solution is to stay warm, Dr. Johnston says. During summer months, that might mean keeping your air conditioner on low, donning mittens before digging around in the freezer for those chicken cutlets and using insulated glasses for chilled drinks. Also, take steps to keep your circulation healthy: Avoid cigarettes and caffeine, both of which narrow blood vessels; stay away from vasoconstricting meds such as decongestants; and hit the gym regularly.
Dark undereye circles
What it might mean: Unless you partied into the wee hours last night, those undereye circles could suggest your allergies are acting up. Allergens can inflame the sinuses and compress nearby blood vessels, causing blood to pool beneath the eyes. "We call the resulting darkness allergic shiners," Dr. Derick says.
Your next step: Pop an antihistamine. Circles still there? Ask your derm about an anti-inflammatory cream such as Elidel.
Yellow eyelid bumps
What it might mean: Your cholesterol is high. When in excess, this fat can collect on your upper lids, forming tiny deposits. And because fat is yellow, so are the spots—you won't miss them, whatever your skin tone, Dr. Johnston says.
Your next step: Have a blood test. If your cholesterol is high—your total count is above 239, your LDL ("bad") cholesterol surpasses 159 or your triglycerides are 200 or higher—eating more produce and whole grains, exercising 30 minutes a day and taking meds can help bring it down. Those lumps may shrink with your cholesterol count; a dermatologist can remove them by scalpel or laser.
Discolored fingernails with slightly blue nail beds
What it might mean: Yellow nails with blue beds can point to diabetes, which impairs blood flow to fingers. "Any woman can have high blood sugar and not notice she has other diabetes symptoms," Dr. Johnston says.
Your next step: Get pricked to find out if your fasting blood sugar is 126 or above (considered diabetic). Losing weight can often drop numbers back into a healthy range, minus the meds, Gidus says. She suggests following a diet that's low in sugar and saturated fats that contains at least 25 grams of fiber daily. And get at least 150 minutes of brisk exercise a week, Dr. Johnston adds. Good advice for all of us!