by Awadh Aljabry
(Abu Dhabi)
QUESTION: I recently found that my blood sugar can rise above 300 mg/dL after eating. A doctor said I have diabetes and prescribed Janumet 50/500 mg. I took three tablets over two days and then stopped. My readings were 134 and 124 mg/dL before breakfast and 242 and 228 mg/dL after breakfast. Do I have diabetes, and can stopping the tablets cause a problem?
Your readings are strongly abnormal and need prompt laboratory confirmation and medical follow-up. A fasting plasma glucose of 126 mg/dL or higher can indicate diabetes when confirmed, while an HbA1c of 6.5% or higher is another diagnostic criterion. Home readings after breakfast of 228–242 mg/dL and a reading above 300 mg/dL are concerning, but an ordinary after-meal home test is not the same as a formal glucose-tolerance test. Stopping Janumet after three tablets does not usually cause withdrawal, but your glucose may remain dangerously high. Contact the prescribing doctor promptly and do not stop, restart, or alter the medicine without medical guidance.
Answer by Dr. Albana Greca, MD, MMedSc
Hello Awadh,
Your doctor may have had laboratory results, symptoms, or examination findings that are not included here. The next step is to confirm exactly which tests established the diagnosis rather than assuming that the diagnosis was made only from one home reading.
Your fasting readings give mixed information. A fasting value of 134 mg/dL is above the diabetes threshold, while 124 mg/dL falls in the prediabetes range. If you did not eat or drink calories for at least eight hours, the elevated result should be confirmed with a laboratory fasting plasma glucose, HbA1c, or another accepted test. Our guide to blood tests used to diagnose diabetes explains these thresholds.
A random plasma glucose of 200 mg/dL or higher together with classic symptoms such as excessive thirst, frequent urination, or unexplained weight loss can establish diabetes. Without clear symptoms or a hyperglycemic crisis, two abnormal laboratory results are generally required. Home glucose meters are useful for monitoring but are not normally used alone to make the diagnosis.
Your readings of 228–242 mg/dL after breakfast are clearly high. However, the diagnostic two-hour cutoff of 200 mg/dL applies to a laboratory oral glucose-tolerance test using a measured glucose drink—not an ordinary breakfast. You can compare typical monitoring goals in our page on blood sugar after meals.
Janumet combines sitagliptin and metformin and is used with nutrition and physical activity to improve glucose control in adults with type 2 diabetes. Whether it is the best first treatment for you depends on the confirmed diagnosis, HbA1c, kidney function, symptoms, other medical conditions, and treatment goals.
Taking only three tablets and then stopping does not normally cause a withdrawal syndrome. The concern is that the medicine cannot control glucose when it is not being taken. Do not double a dose to make up for missed tablets. Contact the prescriber and explain exactly when you took and stopped it, why you stopped, and whether you had nausea, diarrhea, abdominal discomfort, allergy symptoms, or another problem.
Record the time of each reading, whether it was fasting, what you ate, medicines taken, physical activity, and symptoms. A structured blood sugar log will help the clinician interpret the pattern.
Reducing sugary drinks and highly refined foods, choosing balanced portions, and walking regularly are beneficial. You do not need to eliminate all dietary fat or become vegetarian to manage diabetes. Include vegetables, protein, high-fiber carbohydrate, and healthy unsaturated fats in appropriate portions.
Do not judge whether treatment is working after only two days. HbA1c reflects approximately two to three months, and medication decisions should be based on a broader pattern. Lifestyle changes and medication often work together; needing medicine is not a failure.
Do not replace prescribed treatment with “diabetes supplements,” herbal teas, or natural remedies. These products are not proven substitutes for diabetes medicine and may cause interactions or unpredictable glucose changes. Read more about diabetes medications and their safety.
Seek same-day medical advice if glucose repeatedly remains around 300 mg/dL or higher, especially with excessive thirst, frequent urination, weakness, dehydration, or weight loss. Go to emergency care for readings above 400 mg/dL, a meter displaying “HI,” repeated vomiting, abdominal pain, rapid or difficult breathing, confusion, fainting, or inability to keep fluids down. Do not exercise when severely hyperglycemic, dehydrated, or possibly producing ketones.
Please contact the prescribing doctor promptly rather than waiting to see whether diet alone lowers these readings. Ask for the laboratory results that support the diagnosis and a written plan for medication, glucose monitoring, target ranges, and urgent warning signs. A second opinion is reasonable if the diagnosis or instructions remain unclear, but do not leave significant hyperglycemia untreated while arranging it.
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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