Why is there glucose in urine? The causes
Why urine normally contains no glucose
The kidneys reabsorb almost all the glucose filtered from the blood, up to a limit called the renal threshold (on average a blood glucose of ~180 mg/dL). When this threshold is exceeded, or when it is lower than normal, glucose appears in the urine: this is glycosuria.
The most frequent causes
- Diabetes (type 1 or type 2), undiagnosed or uncontrolled: the most common cause. High blood glucose regularly exceeds the renal threshold.
- Prediabetes: blood glucose above normal but not yet diabetic, which can occasionally cause glycosuria.
- Pregnancy: the renal threshold drops naturally; gestational diabetes must still be ruled out.
Temporary and benign causes
- A very sugary meal shortly before the test: blood glucose can briefly exceed the threshold.
- Acute stress, fever or infections: can raise blood glucose for a short time.
- Some medications: corticosteroids can raise blood glucose. A separate case is people taking SGLT2 inhibitors (for diabetes or heart failure): here glucose in the urine is an expected therapeutic effect of the drug, not a finding to interpret.
Renal glycosuria
In some people the renal threshold is lower than normal: glucose appears in the urine even with perfectly normal blood sugar. It is often inherited and benign. (More: renal glycosuria.)
Rare causes
More rarely, glycosuria can be due to kidney conditions such as Fanconi syndrome, or endocrine disorders such as Cushing's syndrome or hyperthyroidism.
How the cause is found
To understand why, a doctor starts with blood tests: fasting glucose, glycated haemoglobin (HbA1c) and, if needed, the glucose tolerance test (OGTT). These distinguish between diabetes, prediabetes, renal glycosuria or temporary causes.
Frequently asked questions
Is glucose in urine after eating normal? After a very large meal, blood glucose can briefly exceed the renal threshold and leave traces of glucose: it is possible, but should still be mentioned to a doctor.
Can stress cause glucose in urine? Yes, acute stress or illness can temporarily raise blood glucose and promote glycosuria.
Can you have glycosuria without diabetes? Yes: pregnancy, renal glycosuria, medications and temporary causes can produce it with normal blood sugar.
Screening at home
Rima GlucoLens lets you run this screening simply and non-invasively, at home, and the app helps you read and interpret the result. It remains a screening tool: assessment and diagnosis always rest with a healthcare professional.
References: World Health Organization (WHO); American Diabetes Association (ADA); MSD Manuals. This article is for information only and does not replace medical advice.
Last updated: July 2026