‘I tested a patient’s urine and it showed sugar. After that, I tested blood sugar and it was 85 mg/dL, which is normal. What is the reason for this?’

‘I tested a patient’s urine and it showed sugar. After that, I tested blood sugar and it was 85 mg/dL, which is normal. What is the reason for this?’

Can urine sugar and blood sugar produce two different results? And what if only one is on the higher side? A Quora query got us thinking on the same lines when a user asked: “I tested a patient’s urine, and it showed sugar. After that, I tested the patient’s blood sugar, and it was 85 mg/dL, which is normal. What is the reason for this?”

Inquisitive, we reached out to Dr Pranav Ghody, a consultant endocrinologist and diabetologist at Wockhardt Hospital, Mumbai Central, who agreed that it “can definitely seem confusing at first”. “Most people will link the presence of sugar in urine to diabetes, but how the body processes sugar is a little more complicated than that,” said Dr Ghody.

Normally, the glucose that is filtered from the blood by the kidneys is almost entirely reabsorbed. “Sugar in urine only occurs when blood sugar levels exceed a certain point (usually 180 mg/dL), which overpowers the kidneys’ reabsorption abilities. So, when blood sugar is 85 mg/dL, which is well within the normal range, we wouldn’t normally expect sugar in urine,” explained Dr Ghody.

There are a couple of possible explanations for this result.

*One possible explanation is that the patient has renal glycosuria, a harmless condition in which the kidneys spill small amounts of glucose into the urine despite normal blood sugar levels. This is due to the kidney’s glucose threshold being set too low. It is not diabetes and doesn’t always need to be treated, said Dr Ghody.

*Another potential reason is the timing of the urine sample. “Perhaps the urine sample was taken some time after a short-lived increase in blood sugar, such as after a large meal, and the sugar was present in the urine at a previous time when the blood test showed normal levels,” said Dr Ghody.

*Also, laboratory variables must be taken into consideration. “False positives may occur due to contamination, improper storage, or certain medications,” noted Dr Ghody.

*Another condition in which mild glycosuria may be present without diabetes is during pregnancy due to increased glomerular filtration, he said.

It must be remembered that a single positive urine sugar test does not confirm the diagnosis of diabetes, stressed Dr Ghody, adding, “Blood sugar tests, either fasting, postprandial, or HbA1c, are still the standard.”

What to do?

If this result keeps popping up, it would not be unreasonable to recheck blood sugar levels, perhaps take a post-meal reading, and look at overall risk factors. However, on its own, normal blood sugar with sugar in urine is not necessarily a reason to sound the alarm, he contended, adding that its all about correlation, not conclusion.

DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.