Urine tests are typically used to detect and monitor urinary tract infections, kidney disease, and other kidney problems, and they’re often included as part of a routine physical. In some instances, glucose can register on urine tests. Anything over .25 mg/mL may be out of the ordinary and could indicate an underlying health issue, but it’s not always cause for concern. Here’s what you should know.
Is it normal to have glucose in the urine?
Your body strives to keep blood glucose within a narrow, steady range—not too high or too low—through a process called glucose homeostasis. And your kidneys play an essential role in this.
When everything works as it should, your kidneys filter your blood and remove glucose. After the blood is filtered, some glucose is returned to the bloodstream via renal transporters. If blood sugar levels go too low, the kidneys can engage in gluconeogenesis. They make additional glucose from other nutrients, such as fat or protein, and release it into the bloodstream.
Because your kidneys return glucose to your blood before waste and excess water are excreted from the body, there shouldn’t be much glucose in your urine. But that’s not always the case.
Eating a lot of carbohydrates can overwhelm the transporters that typically move glucose from the kidneys back into the bloodstream. As a result, excess glucose may stay in the kidneys and spill into the urine. If you have a urine test soon after the meal, it might show glucose in your urine. Provided the level doesn’t consistently exceed 0.8 mmol/L, this isn’t inherently harmful to your kidneys. However, it is a sign that you’ve eaten too many refined carbohydrates and overloaded your system, which doesn’t bode well for your overall metabolic health.
If your level is consistently higher than 0.8 mmol/L—or if you have glucose in your urine despite having fasted for at least eight hours before testing—that’s a problem.
What does it usually mean if you find an abnormal amount of glucose in the urine?
Glucose in your urine means that the kidneys can’t give glucose back to the bloodstream for some reason. This might happen because you’ve eaten so many carbohydrates before testing that the transporters that move glucose back into the blood have hit maximum capacity. It could be a transient issue, but if it happens consistently or your reading is higher than 0.8 mmol/L after fasting, take it seriously.
One possibility, though unlikely, is renal glycosuria. In this rare kidney disorder, too much glucose is removed via urine despite normal blood glucose levels.
More commonly, glucose in urine suggests that you might have Type 1 or Type 2 diabetes (pending confirmation with blood tests). It could also mean that you have kidney disease, either due to diabetes or for an unrelated reason (such as an inherited or autoimmune disease).
Interestingly, certain drugs for Type 2 diabetes called SGLT2 (sodium-glucose Cotransporter-2) inhibitors deliberately push glucose into the urine to bring blood glucose levels down. These medications—which include canagliflozin (Invokana), dapagliflozin (Farxiga), and empagliflozin (Jardiance)—are designed to block the transporters that would otherwise send glucose back into the bloodstream after the blood has been filtered. So if you’re taking one of these drugs and you have glucose in your urine, that’s a sign that the medication is working as intended.
Should people without diabetes or kidney disease worry about glucose in their urine?
Even if you don’t have diabetes or kidney disease, anything besides a transient, minimal amount of glucose in your urine is problematic because it increases the risk of urinary tract infections (UTIs) and a more serious kidney infection.
The urinary tract is susceptible to infection. Bacteria constantly try to come up the urethra (the tube through which urine leaves the body) and cause an infection in the urinary tract. Glucose feeds these bacteria and helps them thrive, which may increase the odds of a UTI.
The pain, burning, and urgency associated with a UTI are bad enough on their own. But the biggest problem occurs when a pathogen makes it all the way up to the kidneys, rather than just infecting the bladder, urethra, or ureters (which connect the kidneys to the bladder). Kidney infections are extremely serious. They may cause fever, pain in the groin or lower back, vomiting, and blood or pus in the urine. Without prompt, proper medical care, they can lead to sepsis and even be fatal.
What should you do if you have glucose in your urine?
The fix for glucose in the urine comes down to the underlying cause. Your doctor will need to order additional tests to determine whether Type 1 or Type 2 diabetes is the cause or something else.
If you don’t have diabetes or kidney disease, but glucose is ending up in your urine, consider it a warning that you’re putting too many refined carbohydrates into your system. Cut carbs, including glucose, and glucose will stop spilling into your urine.
Levels advisor Benjamin Bikman, PhD, is the author of Why We Get Sick. A scientist and professor at Brigham Young University, he studies the role of elevated insulin in obesity and diabetes.