All the Symptoms but Negative Tests

Medically Reviewed


I have all the symptoms for diabetes but the test always comes back negative. Why?


If you have symptoms of diabetes, it's almost 100% likely that testing for diabetes will be positive. As I see it, there are two issues to be tackled in answering your question as to why:

1) What symptoms do you have?

Classic symptoms include extreme thirst, excessive volumes of urine, and hunger (these are called polydipsia, polyuria, and polyphagia in medical jargon). There are lots of other symptoms, and some people have a lot of them, while other folks may have few or no symptoms.

Here's a comprehensive list:

  • extreme thirst, excessive volumes of urine, and hunger
  • fatigue/tiredness
  • nighttime urination
  • blurred vision
  • slow healing of wounds
  • frequent infections, including vaginal yeast infections in women
  • weight loss despite increased appetite (much more common in uncontrolled type 1 diabetes than in type 2)
  • tingling, pain, and/or numbness in the hands or feet
  • dry itchy skin

2) What testing did you have done?

There are basically three tests for diabetes:

  • Urine sugar. A positive test is likely if your blood glucose level has been over 180 mg/dl or thereabouts during the time between the current and previous urination.
  • Blood sugar (AKA blood glucose). A fasting level of 126 mg/dl (7.0 mmol/L) or higher on more than one testing occasion is diagnostic of diabetes. Sometimes BG is measured repeatedly after ingesting a lot of glucose, in what is called a Oral Glucose Tolerance Test (OGTT or GTT); BG values of 200 or higher are abnormal.
  • A1C (this test is also called hemoglobin A1C or glycosylated hemoglobin or HbA1c). A value of 6.5 or more indicates diabetes. The A1C test is influenced by BG changes over a period of about 2 or 3 months, so if your average BG has been high for 3 or more months, your A1C should also be high.

As the NIH points out:

"All laboratory test results can vary from day to day and from test to test. Results can vary

  • within the person being tested. A person's blood glucose levels normally move up and down depending on meals, exercise, sickness, and stress.
  • between different tests. Each test measures blood glucose levels in a different way.
  • within the same test. Even when the same blood sample is repeatedly measured in the same laboratory, the results may vary due to small changes in temperature, equipment, or sample handling.

Although all these tests can be used to indicate diabetes, in some people one test will indicate a diagnosis of diabetes when another test does not. People with differing test results may be in an early stage of the disease, when blood glucose levels have not risen high enough to show on every test."

So, in summary, if you have some of the symptoms I list above, I'd expect you to have elevated values on the tests that I mention. If all these diabetes tests are repeatedly normal, your physician should evaluate you for other conditions, such as diabetes insipidus (which is a separate disease from the diabetes we usually discuss, whose full name is diabetes mellitus).

Answered by William Quick, M.D.