What Causes Dry Mouth in People With Diabetes and How to Treat It

Dry mouth (xerostomia) is an uncomfortable sensation that becomes increasingly common as people age. Low saliva production (hyposalivation) is one of its primary causes. Dry mouth is more than just an unpleasant feeling — it can lead to oral problems and be a major issue for people with diabetes.

What is the link between dry mouth and diabetes?

People with both type 1 and type 2 diabetes are more likely than non-diabetic individuals to report dry mouth. A 2016 systematic review found that 12.5–53.5% of people with diabetes have dry mouth, compared to 0–30% of people without diabetes. The review also found that poorly controlled diabetes was more likely to be associated with dry mouth compared to well-controlled diabetes (although the definition of ‘good’ diabetes control varied between studies).

Diabetes is also associated with hyposalivation. A 2011 study showed that hyposalivation is the most common oral symptom in people with diabetes, affecting up to 68% of people with controlled diabetes and 80% of people with poorly-controlled diabetes (reflected by an elevated hemoglobin A1C level, which is the average amount of glucose on red blood cells over the past 3 months). The 2016 systematic review also revealed that hyposalivation prevalence is higher in people with diabetes (45%) compared to people without it (2.5%).

Not everyone with diabetes will develop a dry mouth. But if you have dry mouth along with other symptoms of diabetes — such as excessive thirst or urination, unintentional weight loss, fatigue, and numbness or tingling in the feet — it is important to get your blood sugar levels checked.

Causes of dry mouth in people with diabetes

Though not completely understood, diabetes can cause dry mouth through multiple biological mechanisms.

Dehydration

People with diabetes often urinate excessively due to the effects of high blood sugar (which causes the kidneys to excrete more water). Without sufficient fluid intake, large quantities of water loss can lead to dehydration and dry mouth. In severe cases, extremely high blood sugar levels can cause complications such as diabetic ketoacidosis and hyperosmolar hyperglycemic syndrome, which commonly presents with dry mouth.

Autonomic neuropathy

The autonomic nervous system regulates automatic body processes, such as heart rate, blood pressure, and breathing. Parasympathetic nerves belong to the autonomic nervous system, and they send signals to the salivary glands to produce saliva. In diabetes, these signals are interrupted, leading to decreased salivary gland function and, consequently, less saliva production. A 2020 study showed that diabetic rats expressed lower levels of parasympathetic receptors in their parotid glands compared to non-diabetic rats, leading to hyposalivation. Administering insulin to control blood sugar levels improved saliva production in the rats. Even though this is an animal study, the results of it provide valuable insights into the mechanism of dry mouth in people with diabetes.

Blood vessel damage

Chronically elevated blood sugar gradually impairs the functioning of the small blood vessels (capillaries) that supply the salivary glands. These blood vessels decrease in density and become more closed to blood flow, meaning that less blood travels to the salivary glands. This reduces their function, leading to decreased saliva production and dry mouth.

Decreased nitric oxide production

Nitric oxide is a vasodilator that plays an important role in salivary gland function by increasing the amount of blood flow to the salivary glands. Without nitric oxide, less blood flow reaches the salivary glands, meaning less saliva production. A 2016 study showed that diabetic rats produced less nitric oxide in their salivary glands, leading to hyposalivation. The findings of this study could potentially provide more knowledge of why people with diabetes are more likely to suffer from mouth dryness.

Increased SGLT1 production

Sodium/glucose cotransporter 1 (SGLT1) is a protein that acts as a water channel in the kidneys as well as the salivary glands. Water moves out of saliva through SGLT1 channels, leading to saliva that is more dry. A 2009 study found that diabetic rats had increased expression of SGLT1, leading to more water leaving the saliva and, therefore, a lower volume of saliva production — such findings could possibly suggest similar mechanisms in humans.

Medication side effects

Over 400 medications include dry mouth as a side effect. Many people with diabetes have related health conditions such as heart disease or complications such as peripheral neuropathy that require treatment with medications (e.g., diuretics, antihypertensives) that cause dry mouth.

Symptoms of dry mouth in people with diabetes

Symptoms of dry mouth among people with diabetes can include any or all of the following:

• Dryness or a feeling of stickiness in the mouth
• A thick, sticky, or stringy appearance to the saliva
• A fissured, cracked appearance of the lips and tongue
• Trouble swallowing, speaking, or chewing
• Bad breath
• Altered taste
• Dry or sore throat
• Hoarseness

People without diabetes may also have dry mouth and hyposalivation due to a long list of other diseases. Some of these include Sjogren’s syndrome, HIV/AIDS, cancer treatment, or psychiatric conditions.

If your dry mouth is due to diabetes specifically, you will likely have other symptoms of diabetes. There is no definitive way to tell from dry mouth alone whether diabetes or another health condition is the underlying cause. Therefore, it is always important to seek medical help to determine what lies at the root of your dry mouth.

Treatment of dry mouth for people with diabetes

Dry mouth treatment in people with diabetes includes a multipronged approach.

The most basic approach includes the prevention of dryness using home remedies. Methods include:

1. Maintaining good hydration by consuming plenty of fluids
2. Swishing the mouth with water or sucking on ice chips
3. Stopping or switching medications that cause dry mouth as a side effect
4. Breathing through the nose rather than the mouth
5. Using a humidifier throughout the day and especially at night
6. Avoiding cold, dry air

It is important to note that drinking fluids too often may be counter-productive as it washes off existing saliva in the mouth. Instead of sipping water regularly, consuming larger quantities on a less frequent basis can help reduce this problem.

Oral hygiene is especially important for people with diabetes and dry mouth because decreased saliva production predisposes to cavities and gum disease. Brushing twice a day with fluoride toothpaste, flossing daily, and seeing the dentist twice a year are important for maintaining proper oral health.

Products for dry mouth for people with diabetes

Besides preventing oral dryness, people with dry mouth and diabetes can use products to stimulate saliva flow. These include sucking on sugar-free candies or lozenges, chewing gum, or consuming lemon juice in small quantities (e.g., drops in water). Look for products containing sorbitol, xylitol, or citrus, which are known to stimulate salivary flow.

If these measures do not provide enough symptom relief, other options include artificial saliva or medications. Artificial saliva, which can be purchased over the counter, usually contains a mix of water and components such as carboxymethylcellulose, polyethylene glycol, sorbitol, and electrolytes to mimic natural saliva. Prescription medications include pilocarpine or cevimeline, which stimulate the action of the parasympathetic nerves to improve saliva production.

Dietary tips to manage dry mouth

To help prevent further drying out the mouth, try to abstain from alcohol, which has a dehydrating effect. Alcohol reduces the level of a hormone called vasopressin. Vasopressin normally causes your body to hold onto water. Therefore, by decreasing vasopressin production, alcohol causes more water to leave the body in the form of urine.

Also, avoid consuming too many dry, salty, sugary, or spicy foods, which can dry out the mouth.

You may want to consider including healthy (low-sugar) sauces, gravies, or dressings to moisten foods and make them easier to swallow. Eating soft, pureed, or moist foods such as yogurt, smoothies, or soups can also help with dry mouth.

Complications of dry mouth with diabetes

Without proper treatment of dry mouth, people with diabetes can experience ongoing discomfort, leading to a poor quality of life. Dry mouth can cause people to eat less than they normally would due to altered taste perception as well as difficulties with chewing and swallowing, which can potentially lead to nutritional deficiencies over time.

Saliva is a complex substance containing small proteins, antibodies, growth factors, hormones, and mucins. These components provide antibacterial, antiviral, and potentially antifungal properties to saliva. Therefore, continuous hyposalivation can result in an increased risk of fungal infections such as candidiasis as well as the promotion of bacteria causing plaque buildup, cavities, tooth decay, and gum disease.

If you are experiencing symptoms of dry mouth, diabetes may be the culprit. However, many other medical conditions and lifestyle behaviors can cause dry mouth, so it is crucial to seek a thorough medical evaluation if your symptoms do not improve with basic strategies such as increasing hydration and making dietary changes. Ultimately, dry mouth in diabetes can be effectively managed through a combination of strategies at home and in collaboration with your doctor.