Researchers studied over 1,600 American adults with diabetes to understand why some develop painful foot ulcers while others don’t. They discovered that people with higher levels of a waste product called blood urea nitrogen (BUN) in their blood were more likely to develop diabetic foot ulcers. The study suggests that doctors might be able to catch foot ulcer problems earlier by regularly checking BUN levels in their diabetic patients. This finding could help prevent serious complications that sometimes lead to amputation.

The Quick Take

  • What they studied: Whether higher levels of a kidney waste product in the blood (called BUN) are connected to diabetic foot ulcers—painful sores that develop on the feet of people with diabetes.
  • Who participated: 1,673 American adults over age 40 with diabetes who participated in a national health survey between 1999 and 2004. About 53% were men, with an average age of 64 years.
  • Key finding: People with the highest BUN levels were 3.5 times more likely to have foot ulcers compared to those with lower BUN levels. This connection appeared to be linear, meaning the higher the BUN, the greater the risk.
  • What it means for you: If you have diabetes, your doctor might want to monitor your BUN levels as part of your regular checkups. Higher BUN could be an early warning sign to take extra care of your feet and get preventive treatment before ulcers develop. However, this is one study, so talk to your doctor about what it means for your specific situation.

The Research Details

This was a cross-sectional study, which means researchers looked at a large group of people at one point in time and compared those with foot ulcers to those without them. They used data from the National Health and Nutrition Examination Survey (NHANES), a well-respected government health study that tracks Americans’ health over time.

The researchers collected information about participants’ BUN levels (measured through blood tests) and whether they had diabetic foot ulcers. They then used statistical models to figure out if higher BUN levels were connected to foot ulcers, while accounting for other factors that might affect the results, like age, weight, and blood sugar control.

They also performed additional analyses to understand exactly how BUN and foot ulcers are related—whether it’s a straight-line relationship or more complicated—and tested whether the connection was different for different groups of people.

This research approach is useful because it looks at real-world data from thousands of people rather than just a handful. By studying people who already have diabetes and checking who has foot ulcers, researchers can identify patterns that might help doctors predict problems before they become serious. The statistical methods used allow them to separate the effect of BUN from other factors that could also cause foot ulcers.

This study has several strengths: it included a large, diverse group of Americans, used standardized health measurements, and applied rigorous statistical methods. However, because it’s cross-sectional (a snapshot in time), we can’t prove that high BUN actually causes foot ulcers—only that they’re connected. The study is based on data from 1999-2004, so some findings might not apply to today’s population or treatments. Additionally, only about 8% of participants had foot ulcers, which is a relatively small number for this type of analysis.

What the Results Show

The main finding was striking: people with the highest BUN levels had 3.56 times the risk of having a diabetic foot ulcer compared to those with lower levels. This relationship appeared to follow a straight line—meaning as BUN goes up, foot ulcer risk goes up proportionally.

The researchers identified a threshold point at 5.4 mmol/L of BUN. Below this level, the risk was lower; above it, the risk increased. This suggests there may be a specific BUN level that doctors should watch for as a warning sign.

When the researchers looked at different groups of people (by age, sex, weight, and blood sugar control), the connection between BUN and foot ulcers remained consistent. This suggests the relationship isn’t just happening in one type of person but appears across different populations.

Out of 1,622 participants studied, 131 people (about 8%) had diabetic foot ulcers. Among those with the highest BUN levels, the percentage with foot ulcers was noticeably higher than among those with lower BUN levels.

The analysis showed that the relationship between BUN and foot ulcers was nearly linear (straight-line), though there was a small possibility it could be slightly curved. This consistency suggests a genuine biological connection rather than a random pattern. The fact that the relationship held true across different age groups, both men and women, and people with different weights suggests this isn’t a fluke finding limited to one type of person.

This is one of the first studies to specifically examine the connection between BUN levels and diabetic foot ulcers. Previous research has shown that kidney function problems are common in people with diabetes and can contribute to various complications. This study adds to that knowledge by suggesting that BUN—a marker of kidney function—might be a useful early warning sign for foot ulcer development. The findings align with what we know about how kidney problems can affect wound healing and blood flow.

This study has important limitations to consider. First, it’s based on data from 1999-2004, so it may not reflect current diabetes care or populations. Second, because it’s a snapshot study, we can’t prove that high BUN causes foot ulcers—only that they’re connected. Third, the study didn’t include information about how people were treating their diabetes or managing their feet, which could affect results. Fourth, only 8% of participants had foot ulcers, which is a small number for this type of analysis. Finally, the study only included Americans over 40, so results might not apply to younger people or other populations.

The Bottom Line

If you have diabetes, ask your doctor to monitor your BUN levels as part of your regular health checkups. If your BUN is elevated (above 5.4 mmol/L), take extra precautions with foot care: check your feet daily for sores or changes, keep them clean and dry, wear proper shoes, and see a podiatrist regularly. These recommendations are based on moderate evidence—the study is solid, but more research is needed to confirm these findings. Don’t make major changes to your diabetes treatment based solely on this study; discuss any concerns with your healthcare provider.

This research is most relevant for people with diabetes, especially those over 40. It’s also important for doctors and nurses who care for diabetic patients. If you have diabetes and a history of foot problems, this information is particularly valuable for you. People without diabetes don’t need to worry about this connection. If you have kidney disease or elevated BUN for other reasons, talk to your doctor about whether this applies to you.

Changes in foot ulcer risk based on BUN levels would likely develop over weeks to months, not overnight. If your BUN is high, the increased risk doesn’t mean you’ll definitely get a foot ulcer—it just means you should be more vigilant. With proper foot care and management of your diabetes and kidney health, you may be able to prevent ulcers from developing. If you do develop early signs of foot problems, catching them quickly through regular monitoring could prevent serious complications.

Want to Apply This Research?

  • Track your BUN levels at each doctor’s visit and record the date and value. Set a reminder to check your feet daily and log any changes, redness, swelling, or sores you notice. Create a simple chart showing your BUN trend over time to discuss with your doctor.
  • Use the app to set daily foot care reminders: inspect feet each morning and evening, keep a log of any concerns, and schedule regular podiatrist appointments. If your BUN is elevated, increase the frequency of foot checks and set alerts to prompt more frequent doctor visits for monitoring.
  • Check BUN levels at least twice yearly (or as recommended by your doctor) and track the results in the app. Maintain a running log of any foot problems, treatments received, and how they resolved. Share this data with your healthcare team to help them identify patterns and adjust your care plan as needed.

This research suggests a connection between BUN levels and diabetic foot ulcers, but it does not prove that high BUN causes foot ulcers. This study is based on data from 1999-2004 and may not reflect current medical practice or populations. Do not use this information to diagnose or treat yourself. Always consult with your healthcare provider before making changes to your diabetes management, foot care routine, or any medical treatment. If you have diabetes, work with your doctor to develop a personalized prevention and care plan based on your individual health situation. This article is for educational purposes only and should not replace professional medical advice.