What Do the Half-Moons on Your Nails Mean?

Take a moment to look at your nails. You see those half-moon circles at the base of them? In most cases, they’re not a cause for concern. They’re simply a part of your nail matrix where new nail growth occurs.

But if you ever notice significant changes in their color or size while also dealing with other symptoms, you may need to bring these concerns to a doctor.

Internal medicine physician Manjaree Daw, MD, explains just what those half-moons mean and walks us through some of their characteristics and common changes.

What is the moon-shaped part of your nail?

The half-moon circle you see at the base of your nail is called a lunula. Lunulae (plural) tend to look clear or white and can be more prominent on some fingers and less prominent on others. For example, they’re usually larger on your thumb or big toe. They also tend to be more noticeable when we’re young and usually get smaller with age. But in terms of function, they’re simply a visible part of the matrix underneath your nail where new cell growth occurs.

What if you don’t have one?

Everyone has lunulae, but they may not always be visible. If you don’t see them, there’s usually no cause for concern, especially if you’re not experiencing any other symptoms. It may just be hidden underneath your cuticle or it may have decreased in size as you got older.

What does the lunula say about your health?

As lunulae exist where the newest nail cells are growing, certain characteristics may occasionally provide clues to your overall health. To understand why this is the case, Dr. Daw compares it to other seemingly innocuous characteristics that pop up whenever your body undergoes other physiological changes.

“People with celiac disease who are allergic to gluten often think of it as just a GI disease that causes an upset stomach. But celiac disease can have extra-intestinal manifestations where it affects your skin and causes blisters,” illustrates Dr. Daw.

On the surface, the blisters may not be noticeably linked to celiac disease unless a person is also dealing with symptoms of a flare-up, like gastrointestinal upset or diarrhea. But when looked at together, a doctor may recognize the diagnosis.

“Systemic diseases can manifest in different parts of the body,” she adds. “So, we have to look at everything together in order to make informed decisions.”

Color

“The color of your lunulae comes from what’s deposited by the living tissue in your nail matrix,” explains Dr. Daw. “If you have any toxins running throughout your body, these could get deposited into your nail matrix and affect their appearance.”

Some lunulae colors are occasionally associated with the following conditions:

• Red: Cirrhosis, lung disease or heart failure
• Blue: Wilson’s disease, diabetes or silver poisoning
• Brown: Chronic kidney disease or kidney failure
• White: Kidney disease or Terry’s nails
• Yellow: Tetracycline therapy or yellow nail syndrome

At face value, these changes in your lunulae might appear concerning. But Dr. Daw cautions not to take these alterations in your nail bed as pure fact unless you’re experiencing symptoms that actually give you cause for concern for those specific conditions.

“These changes are often esoteric [obscure] because you wouldn’t diagnose any disease just from looking at your lunulae,” she clarifies.

Changes in size

In some circumstances, lunulae could decrease in size if you have anemia or are dealing with malnutrition. But like with other conditions, again, Dr. Daw cautions against worrying about these subtle changes unless you have other symptoms that lend themselves to these conditions. This is important to remember, particularly because everyone’s lunulae are different and tend to decrease with age over time.

When should you talk to your doctor about half-moon nails?

“If you notice any changes to your body and you’re experiencing symptoms or feel like it’s an important concern, bring those concerns to your physician and ask for an explanation,” advises Dr. Daw.

“It could be something very innocuous and not matter or it could be something more serious. But that’s why we’re here — to guide you toward those answers and provide treatment if it’s necessary.”