Glucose, or blood sugar, is the primary source of energy for the body. Maintaining its concentration within a narrow range is important for health. A single blood sugar reading, such as 135 milligrams per deciliter (mg/dL), must be placed within the context of when the test was performed. The meaning of this number changes drastically depending on the circumstances of the test.
Types of Blood Glucose Testing
Healthcare professionals rely on several standardized tests to measure blood glucose levels, each with different reference ranges. The Fasting Plasma Glucose (FPG) test is performed after you have had no caloric intake for at least eight hours, typically overnight. This test is designed to measure your body’s baseline glucose control without the influence of recent meals. Normal fasting values fall between 70 and 100 mg/dL.
Another common measurement is the Postprandial Glucose test, taken two hours after a meal. This timing captures the peak glucose response to food and assesses how effectively insulin clears sugar from the bloodstream. For individuals without diabetes, this reading is normally below 140 mg/dL. The Random Glucose Test is the third type, which is taken at any time of day without regard to when you last ate. This test is often used during a routine check-up or when a patient presents with symptoms of high blood sugar.
Interpreting a Reading of 135
A reading of 135 mg/dL is interpreted differently depending on the test type. If 135 mg/dL was obtained during a Fasting Plasma Glucose test, it is considered high and falls outside the normal range (70–100 mg/dL). A fasting result between 100 and 125 mg/dL indicates impaired fasting glucose (prediabetes). Since 135 mg/dL is above the 126 mg/dL threshold, a single reading at this level meets the diagnostic criterion for diabetes.
Conversely, if the 135 mg/dL result was taken two hours after a meal, it is considered a healthy reading. The postprandial goal for most non-diabetic adults is below 140 mg/dL, meaning 135 mg/dL is within the expected normal post-meal spike. This demonstrates effective processing of consumed carbohydrates. If 135 mg/dL was a Random Glucose Test, it is not immediately concerning unless symptoms of high blood sugar are present. A random reading is only diagnostic for diabetes if it is 200 mg/dL or higher alongside symptoms like unexplained weight loss or excessive thirst.
What to Do Next
A single blood glucose measurement is not sufficient to diagnose prediabetes or diabetes. If your 135 mg/dL reading was taken in a fasting state, contact a healthcare provider for confirmatory testing. Diagnosis requires two separate abnormal test results, either from the same test on different days or from two different types of tests.
The next step will likely involve a repeat of the FPG test or a different laboratory test called the Hemoglobin A1C. The A1C test provides a measurement of your average blood glucose level over the previous two to three months.
While waiting for your appointment, keep a detailed log of your readings, including the time and what you ate beforehand. Maintaining good hydration is also helpful, as dehydration can artificially concentrate blood glucose levels. The 135 mg/dL reading should prompt you to seek professional guidance and clarify your metabolic status.