Blood sugar, or glucose, is the primary sugar circulating in your bloodstream, acting as the main energy source for your body’s cells and tissues. The body regulates glucose using the hormone insulin, which moves glucose from the blood into the cells. Blood sugar levels are measured in milligrams per deciliter (mg/dL). A reading of 135 mg/dL can provoke concern, but whether it is considered “high” depends entirely on the context of when the measurement was taken.
Interpreting 135: Context Matters
The meaning of a 135 mg/dL reading is highly variable and hinges on whether the measurement was taken while fasting, post-meal, or at a random time. If taken after an eight-hour fast, 135 mg/dL falls into a concerning range. This level is above the threshold for prediabetes (100–125 mg/dL) and meets the criteria generally used to diagnose diabetes, which begins at 126 mg/dL.
Conversely, if the 135 mg/dL measurement was taken two hours after the start of a meal, it is typically considered within a healthy range. For healthy individuals, glucose levels commonly peak within an hour of eating and should return to below 140 mg/dL within two hours. A reading of 135 mg/dL two hours post-meal suggests the body is managing the carbohydrate load effectively.
For a random measurement taken at any time, 135 mg/dL is not immediately alarming, especially if a meal or snack was consumed recently. However, a random reading of 200 mg/dL or higher, especially with symptoms, is a strong indicator of diabetes.
Standard Blood Sugar Ranges
The medical community uses specific numerical cut-offs, measured using plasma glucose tests, to classify blood sugar status.
Normal Ranges
A normal fasting plasma glucose level is considered below 100 mg/dL. During an Oral Glucose Tolerance Test (OGTT), a normal result two hours after consuming a glucose solution is less than 140 mg/dL.
Prediabetes
Prediabetes begins when the body shows a reduced ability to process glucose, but levels are not yet high enough for a diabetes diagnosis. Impaired Fasting Glucose is classified as a fasting level between 100 mg/dL and 125 mg/dL. Impaired Glucose Tolerance is indicated by an OGTT result between 140 mg/dL and 199 mg/dL two hours after consumption. Prediabetes is also identified by a Hemoglobin A1c (HbA1c) result between 5.7% and 6.4%, which reflects the average blood sugar level over the past two to three months.
Diabetes
A diagnosis of diabetes is typically confirmed with a fasting plasma glucose level of 126 mg/dL or higher on two separate occasions. Alternatively, diagnostic criteria are met with an OGTT result of 200 mg/dL or higher, or an HbA1c of 6.5% or more. A single random plasma glucose measurement of 200 mg/dL or higher accompanied by symptoms also suggests a diagnosis.
Immediate Next Steps and Recurrent Readings
A single reading of 135 mg/dL, particularly if fasting, warrants a prompt discussion with a healthcare provider. A single data point is not sufficient to establish a chronic condition, as diagnoses require confirmatory testing. Consulting a medical professional helps determine the necessary follow-up steps and places the reading into proper context.
The doctor will likely order additional, definitive tests to confirm the result and assess long-term glucose control. These typically include a repeat fasting plasma glucose test to verify the initial finding. An HbA1c test may also be ordered, which provides an estimate of your average blood sugar over the preceding months, offering a broader picture than a single-moment reading.
A single, unexpected high reading is a signal to investigate further. The primary action is to seek professional medical advice rather than attempting to self-diagnose or make drastic lifestyle changes without clinical guidance. Your healthcare team can interpret the full scope of your health history and test results.
Factors Influencing Temporary Spikes
Several non-chronic physiological and environmental factors, beyond food intake, can temporarily elevate blood sugar levels into the 135 mg/dL range.
Periods of acute mental or physical stress trigger the release of hormones like cortisol and adrenaline. These stress hormones signal the liver to increase glucose production, preparing the body for a “fight-or-flight” response, which raises blood sugar.
Illness or infection, even a common cold, causes the body to release similar stress hormones to fight the infection, leading to a temporary spike in glucose. Certain medications, such as corticosteroids (often used for inflammation), can also cause a significant increase in blood sugar as a known side effect. The use of these medications can push a reading to 135 mg/dL or higher in an otherwise healthy person.
Poor or insufficient sleep can disrupt the body’s ability to use insulin effectively, leading to increased insulin resistance and higher morning glucose readings. Intense, short-term physical exertion can also temporarily raise blood sugar as the body mobilizes stored glucose for immediate energy. These temporary fluctuations highlight why one-off readings must be evaluated alongside a person’s recent activities and health status.