by Rondal
(Somerset KY U.S.A)
QUESTION: One hour after I ate, my blood sugar was 347 mg/dL. Should I be worried?
A glucose reading of 347 mg/dL one hour after eating is dangerously high and is not an acceptable normal response to a meal. Wash and dry your hands, then repeat the test once with a fresh strip. If it remains at or above 300 mg/dL, contact urgent medical care now. Go to an emergency department or call 911 for vomiting, abdominal pain, rapid or difficult breathing, fruity-smelling breath, confusion, severe weakness, fainting, dehydration, or moderate or high ketones.
Answer by Dr. Albana Greca, MD, MMedSc
Hi Rondal,
Yes, this reading should be taken seriously. Blood glucose normally rises after eating, but 347 mg/dL is far above the usual post-meal target. For many nonpregnant adults with diabetes, a common individualized goal is below 180 mg/dL one to two hours after the meal begins.
If you are awake, not vomiting, and have not been told to restrict fluids, sip water while arranging medical advice. Avoid regular soda, juice, energy drinks, and other sugary beverages.
Glucose may be near its post-meal peak at one hour, but 347 mg/dL is still markedly abnormal. A one-hour reading after an ordinary meal is not a standard diagnostic test, and waiting for a two-hour result does not make the first result harmless. You can compare common monitoring targets on our page about blood sugar after eating.
Possible causes include undiagnosed diabetes, a high-carbohydrate meal or sugary drink, missed or insufficient diabetes medicine, infection, pain, emotional or physical stress, dehydration, corticosteroid treatment, or a problem with insulin delivery. A contaminated finger or damaged test strip can also produce an inaccurate result, which is why one careful repeat is useful.
A home meter cannot diagnose diabetes by itself. However, a laboratory random plasma glucose of 200 mg/dL or higher with classic symptoms such as excessive thirst, frequent urination, or unexplained weight loss can establish diabetes. Without clear symptoms, diagnosis usually requires confirmatory laboratory testing.
Arrange a fasting plasma glucose and laboratory HbA1c. An HbA1c estimates average glucose over approximately the previous two to three months. Our guide to diabetes blood tests and diagnostic ranges explains how these tests are interpreted.
Write down the time, result, meal, medicines, symptoms, and repeat measurement. Bring your meter and strips to the appointment so the reading can be compared with a laboratory result. A structured blood sugar log can help your clinician identify whether the rise is persistent.
Seek emergency care if glucose remains at or above 300 mg/dL and you have vomiting, abdominal pain, rapid or deep breathing, fruity-smelling breath, confusion, severe drowsiness, fainting, inability to keep fluids down, or moderate or high ketones. These may be signs of diabetic ketoacidosis or another hyperglycemic emergency.
A reading of 347 mg/dL should never be described as acceptable simply because it occurred after eating. If you have no diabetes diagnosis, arrange same-day medical assessment. If you already have diabetes, follow your written high-glucose plan and contact your diabetes team because treatment may need review.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical advice, diagnosis, or treatment. Do not start, stop, or change medicines, supplements, diet, or exercise plans without speaking with your healthcare provider.
Last reviewed: July 2026.
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