A scalloped tongue has wavy, rippled indentations along its edges where the tongue presses against the teeth. It’s not a disease on its own but a physical sign that something is making your tongue swell, pushing it outward, or causing you to press it against your teeth habitually. The causes range from completely harmless to medically significant, so the indentations themselves are less important than what’s behind them.
How Scalloping Forms
Your tongue sits inside an arch of teeth. When the tongue is its normal size and resting in a relaxed position, it fits comfortably without pressing against anything. But if the tongue swells even slightly, or if you habitually push it against your teeth, the edges mold around those teeth over time. The result is a row of small, rounded dents along the sides, sometimes called crenated tongue or lingua indentata in clinical settings.
The indentations are usually painless. You might not even notice them until you look in the mirror or a dentist points them out. Occasionally the edges feel tender or slightly sore, especially if there’s underlying inflammation.
Common Causes
Vitamin and Mineral Deficiencies
Low levels of B12, iron, niacin, or riboflavin can cause the tongue to swell and become inflamed, a condition called glossitis. The swollen tongue then presses into the teeth and picks up their shape. This is one of the most common and most easily fixable causes. If your diet is limited, you’ve had recent digestive issues affecting nutrient absorption, or you follow a strict vegan or vegetarian diet without supplementation, deficiency is worth investigating.
Hypothyroidism
An underactive thyroid slows your metabolism and causes a buildup of certain sugary molecules in tissues throughout the body, including the tongue. This makes the tongue physically larger. Hypothyroidism from conditions like Hashimoto’s thyroiditis can produce noticeable tongue swelling with clear teeth marks along the edges, sometimes accompanied by a deep central fissure running down the middle of the tongue. Other signs you might notice alongside the scalloping include fatigue, weight gain, dry skin, and feeling cold more than usual.
Dehydration and Fluid Retention
This one cuts both ways. Dehydration can cause mild tongue swelling, but so can fluid retention from high sodium intake or hormonal fluctuations. If you notice the scalloping looks worse on some days than others, fluid balance may be playing a role.
Clenching, Grinding, and Tongue Thrusting
Not all scalloped tongues are swollen. Some people develop the indentations purely from mechanical pressure. If you clench your jaw during the day, grind your teeth at night (bruxism), or have a habit of pressing your tongue firmly against your teeth, the constant force is enough to leave marks. Stress and anxiety tend to worsen these habits, and many people do them unconsciously. You might notice the scalloping is more prominent during high-stress periods or after a poor night’s sleep.
Sleep Apnea
The relationship between a scalloped tongue and obstructive sleep apnea is more nuanced than many sources suggest. A 2025 study published in Frontiers in Sleep found no statistically significant link between scalloped tongue and obstructive sleep apnea in general. However, the same study found that scalloped tongue tripled the odds of severe obstructive sleep apnea specifically, with an odds ratio of about 3.1. When a scalloped tongue appeared alongside a neck circumference of 40 cm (roughly 15.7 inches) or greater, the risk of severe disease jumped even higher, with an odds ratio of 4.2.
In practical terms, a scalloped tongue alone doesn’t predict sleep apnea, but combined with other red flags like loud snoring, daytime sleepiness, and a thicker neck, it adds a meaningful piece to the picture. The study also found that people with scalloped tongues experienced about 6 to 7 more oxygen drops per hour during sleep, suggesting their airways were partially collapsing more frequently.
Less Common but Serious Causes
Amyloidosis is a rare condition where abnormal proteins build up in organs and tissues. One of its hallmark signs is an enlarged tongue that sometimes looks rippled along its edge. The Mayo Clinic lists this rippled appearance as a recognizable feature of the disease. Amyloidosis affects multiple organ systems and produces other symptoms like unexplained weight loss, swelling in the legs, numbness or tingling in the hands and feet, and fatigue. A scalloped tongue in isolation is extremely unlikely to be amyloidosis, but if you’re experiencing a cluster of these other symptoms, it’s worth bringing up.
Allergic reactions and certain autoimmune conditions can also cause enough tongue swelling to create scalloping, though these typically come with more obvious symptoms like pain, redness, or difficulty swallowing.
How Doctors Figure Out the Cause
There’s no single test for “scalloped tongue.” Instead, your doctor works backward from the symptom to identify what’s driving it. The process usually starts with a conversation about your overall health, recent changes, and any other symptoms you’ve noticed. From there, blood tests can check for vitamin deficiencies, thyroid hormone levels, and markers of inflammation or unusual protein levels. If something looks abnormal, a small tissue biopsy of the tongue may help clarify the diagnosis.
If sleep apnea is suspected based on your symptoms and physical build, a sleep study is the standard next step. Your doctor may also examine your jaw alignment and ask about clenching or grinding habits, sometimes referring you to a dentist for further evaluation.
What Fixes It
Because scalloped tongue is a symptom rather than a condition, treatment depends entirely on the underlying cause. Correcting a B12 or iron deficiency with supplements or dietary changes can resolve the swelling, and the indentations gradually smooth out as the tongue returns to its normal size. Thyroid hormone replacement for hypothyroidism works the same way, though it may take weeks to months before the tongue visibly changes.
For clenching and grinding, a night guard protects both the teeth and the tongue, and addressing stress or anxiety can reduce the unconscious pressure. If sleep apnea is diagnosed, treatment with a continuous positive airway pressure device or an oral appliance can improve breathing and may reduce the tongue swelling over time.
Staying hydrated and keeping sodium intake reasonable helps if fluid imbalance is contributing. In most cases, once the root cause is managed, the scalloping fades on its own. The tongue heals relatively quickly compared to other tissues, so visible improvement often shows up within a few weeks of effective treatment.