Yes, both a nutritious diet and growth-encouraging hair care practices are essential for maintaining healthy locks. But sometimes hair loss is a disease’s early warning sign. If so, better to consult a physician than a stylist. How do you know the difference or what to look out for? Coco & Crème reports on the top five disease diagnoses that may explain why your hair’s thinning or—yikes!—falling out.

Anemia. This iron deficiency is one of the most common medical reasons for hair loss. (Many women develop anemia during pregnancy.) Low iron levels reduce the number of the body’s red blood cells and often lead to fatigue. What this means for hair is that the body’s lack of iron weakens hair follicles and that results in hair loss. Although it’s best to consult a physician if you think you have anemia, preventive measures include taking vitamin supplements or eating more iron-rich foods, such as fish, wheat germ and dark green leafy vegetables. (Click here for more about healthy-hair foods.)

Thyroid disease. There are two types: hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid). Both can cause rapid hair loss. The thyroid gland, located in the neck, produces hormones that help control metabolism and growth. When the thyroid supplies insufficient amounts of these hormones, thyroid disease occurs. (To read more about other symptoms of thyroid disease, click here.)

Diabetes. This hormone-related disease is most commonly known as the body’s inability to properly process glucose (sugar), but it can also cause hair loss. People with diabetes are sensitive to skin and hair problems because their blood circulation is not optimal and they’re unable to regrow hair at a normal rate. As diabetes progresses, hair thinning worsens. If you suffer from early diabetes symptoms, it’s important to consult a physician as soon as you notice signs of the disease. Also, don’t just monitor your diabetes for your hair’s sake; it’s a life-or-death issue. (Click here to read about how actor Anthony Anderson discovered he had type 2 diabetes.)

Ringworm of the scalp. When a type of fungus called dermatophytes grows on your scalp, it results in this topical fungal infection. But it can also occur on your skin and nails. This itchy condition has a host of unpleasant symptoms that include chunks of hair falling out, oozing pus, flaking and scaling of the scalp, redness and blisters. Ringworm of the scalp—the name comes from the fact that the fungus often grows in ring patterns—is a highly contagious skin infection. It can be transmitted through person-to-person contact, animal-to-person contact or object-to-person contact. What’s more, ringworm of the scalp accounts for 50 percent of hair loss experienced by children. To treat the yucky condition, docs prescribe an anti-fungal pill. (Click here to learn what scaly yellow patches on your baby’s scalp might mean.)

Lupus. This auto-immune disorder causes the body to attack its own healthy cells, tissues and organs. Lupus creates inflammation, and that affects many different systems in the body, including skin and hair. Hair loss is often an early warning sign of lupus, and shedding can be patchy or extreme. After lupus patients are treated, hair re-growth can proceed, but the going is slow. For reasons still not understood, women of color are two to three times more likely to develop the disorder. To get tested for lupus, visit a doctor for a urine or blood test. (Click here for one woman’s story about how hair loss signaled she had lupus.)