A Hidden Tooth Infection May Be Disrupting Your Blood Sugar, Scientists Find

Deep tooth infections can quietly fuel inflammation that disrupts blood sugar control, and treating them may benefit overall metabolic health.

For many years, in Vikram Niranjanas’s work as a public health dentist and researcher, he noticed a recurring trend. Patients with deep infections at the root of a tooth often also struggled with broader health issues, especially diabetes. At the time, the connection was unclear. New research is now shedding light on this relationship, showing that treating a deep tooth infection may also support better blood sugar control.

Although a tooth infection may seem limited to the mouth, its impact can extend throughout the body. Recent studies have shown that people who received root canal treatment for long-standing infections at the tip of the tooth root had lower blood sugar levels and reduced inflammation during the two years that followed.

This pattern was reinforced by a longitudinal metabolomic analysis, a type of study that follows individuals over time and relies on detailed blood testing to track hundreds of small molecules linked to bodily function. By using this approach, researchers were able to see how treating a dental infection affected overall metabolism, rather than just resolving the problem in the tooth.

Treating teeth changes whole-body metabolism

The people included in the metabolic analysis were diagnosed with apical periodontitis, a serious infection that develops around the tip of a tooth root. Because it usually causes little or no discomfort, many individuals are unaware of the problem until it is detected on an X-ray during a dental exam.

Blood samples taken before and after treatment revealed improvements in long-term blood sugar levels, along with changes in markers associated with heart and metabolic health. Removing the infected tissue from inside the tooth appeared to have positive effects well beyond the mouth.

These benefits may occur because such infections are not always confined to the tooth itself. When bacteria spread into the surrounding tissues, the immune system is activated. If the infection continues over time, it can trigger low-grade inflammation: a persistent immune response that remains active rather than resolving.

This ongoing inflammation can enter the bloodstream and affect the rest of the body. It can interfere with normal blood sugar control because chronic inflammation interferes with insulin function, making it more difficult for cells to take up sugar from the blood.

To better explain how a localized dental infection might influence overall health, researchers have reviewed the existing evidence. In a narrative review, they brought together results from multiple studies and outlined the biological pathways that could connect apical periodontitis with broader systemic disease.

Oral infections and diabetes

Many studies have explored this connection between oral infections and diabetes, and these findings can be summarized more simply. A review of seven studies found that people with diabetes are more likely to have persistent lesions around root-treated teeth.

In this case, it is diabetes that increases the risk of slow healing – not the other way around. High blood sugar weakens the immune response and disrupts bone repair, so lesions at the tip of the root (seen on X-rays as darker areas where bone has not healed properly) are more common.

Another review found that people with diabetes also face a higher risk of developing new apical periodontitis in root-filled teeth compared with people without diabetes. A clinical study involving hundreds of root-filled teeth reported the same trend.

Patients with diabetes had more persistent lesions than those without, reflecting poorer glycaemic control – meaning blood sugar levels remain consistently higher than recommended, something known to slow healing throughout the body, including in bone and connective tissue.

More information on this connection can be found in clinical guidelines from diabetes and oral-health organisations, and in research on wound healing and glycaemic control, which all highlight how high blood sugar impairs immune function and tissue repair.

Treating infection improves metabolic markers

Researchers are now studying what happens when these infections are treated successfully. One study using detailed metabolic testing found that root canal therapy not only resolved the infection but also led to better blood sugar control and reductions in inflammatory markers.

Root canal treatment removes the infected tissue and seals the space, stopping bacteria and toxins from affecting surrounding tissues. Another study confirmed that while lesions in root-treated teeth heal more slowly in people with diabetes, they do improve once the infection is managed. Even gradual healing seems to benefit the body as a whole.

These findings echo what we know about gum disease. Treating gum infections can improve blood sugar control in people with diabetes, a relationship supported by studies showing that periodontal therapy – professional treatment to remove plaque, tartar and infection from below the gumline – modestly reduces HbA1c levels.

HbA1c is a measure of average blood sugar over several weeks, so even a small reduction indicates improved long-term glucose control. Scientists suggest that reducing chronic inflammation in the mouth may help the body regulate sugar more effectively.

Hidden infections with outsized effects

What makes infections at the tip of the tooth root so interesting is how easy they are to miss. Unlike gum disease, which often causes pain, swelling, or bleeding, apical infections can exist silently, while inflammation quietly spreads through the body. Reviews of apical periodontitis emphasize how often it goes unnoticed.

None of this means that root canals are a treatment for diabetes. The changes observed in studies are moderate and depend on factors such as infection severity and overall health.

And researchers are clear that causality is not yet established, so more controlled trials are needed. But the research strongly suggests that oral health has a wider role in metabolic health than most people realize.

For people with diabetes or at risk of it, this connection matters. A painful tooth, or even one that simply feels different, could be more than a local problem.

These findings also highlight a bigger issue, which is that dental care and medical care are often treated as separate worlds. The research on root canal infections shows how closely linked they can be. A properly treated tooth can save more than a smile; it may contribute to better overall health.

Adapted from an article originally published in The Conversation.

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