Normal blood sugar levels 88, 81, 90 and A1C=6

by Arti





QUESTION: My fasting glucose results were 88 mg/dL in May, 81 in August, and 90 in October, but my HbA1c is 6.0%. Why are my fasting readings normal while the HbA1c is higher? Does this mean I have diabetes?





Quick Answer


Your fasting glucose readings are in the normal laboratory range, but an HbA1c of 6.0% is in the prediabetes range—not the diabetes range. This difference can occur because fasting glucose measures one moment, while HbA1c reflects average glucose over about three months and may detect higher readings after meals or at other times. Repeat the HbA1c with a laboratory test and discuss whether fasting glucose or a two-hour oral glucose tolerance test is needed.




Answer by Dr. Albana Greca, MD, MMedSc



Hi Arti,



Your results are not contradictory. They measure different parts of glucose metabolism, and it is possible to have normal fasting glucose with an HbA1c in the prediabetes range.



What Does an HbA1c of 6.0% Mean?



For a nonpregnant adult, HbA1c is interpreted as follows:




  • Below 5.7%: normal range

  • 5.7–6.4%: prediabetes range

  • 6.5% or higher: diabetes range when confirmed



An HbA1c of 6.0% corresponds to an estimated average glucose of about 126 mg/dL. This does not mean that glucose stays at 126 all day. Some readings may be lower before breakfast and higher after meals.



Why Can Fasting Glucose Be Normal?



Fasting glucose is a snapshot taken after at least eight hours without calories. Your values of 81, 88, and 90 mg/dL are within the normal fasting range of below 100 mg/dL.



HbA1c reflects glucose exposure across the day and night. It can be higher because of:




  • Glucose rises after meals that are not seen in fasting tests

  • Higher readings on days between the three fasting tests

  • Recent changes in weight, food, activity, sleep, stress, or illness

  • Normal biological and laboratory variation



A few normal fasting results therefore cannot describe every glucose level from the previous three months.



Does This Mean You Have Diabetes?



No. An HbA1c of 6.0% does not meet the diagnostic threshold for diabetes. It does indicate increased risk of developing type 2 diabetes and cardiovascular disease over time.



Prediabetes often causes no symptoms. The absence of excessive thirst, frequent urination, or weight loss does not make the HbA1c result normal and does not rule out prediabetes.



Should the HbA1c Be Repeated?



Yes. When an abnormal result is found in someone without clear symptoms, repeat testing is appropriate. The repeat should be performed by a laboratory using a standardized method. Your clinician may repeat HbA1c, obtain a fasting plasma glucose, or use a two-hour 75-gram oral glucose tolerance test.



The glucose tolerance test may be useful when HbA1c and fasting glucose do not agree because it can identify impaired glucose handling after a glucose drink.



Could the HbA1c Be Inaccurate?



Sometimes. HbA1c depends on the lifespan and type of red blood cells as well as glucose. Iron-deficiency anemia, recent blood loss or transfusion, kidney or liver disease, and some hemoglobin variants can produce misleading results.



Hemoglobin variants are more common in people with African, Mediterranean, Middle Eastern, South Asian, or Southeast Asian ancestry. They do not always interfere, because the effect depends on the laboratory method.



If repeat HbA1c remains higher than expected, ask whether a complete blood count, iron studies, kidney or liver tests, or a hemoglobin-variant review is appropriate. Do not assume the HbA1c is false without evidence.



Could Vitamin C Explain It?



Ordinary dietary vitamin C is not a reliable explanation for an HbA1c of 6.0%. High-dose supplements can interfere with some glucose or HbA1c methods, but the direction and size of the effect depend on the test. Tell the clinician and laboratory about all supplements instead of trying to correct the result yourself.



What Should You Do Now?




  • Arrange repeat laboratory testing rather than checking fasting glucose excessively at home.

  • Ask whether a two-hour oral glucose tolerance test would clarify the difference.

  • Review family history, waist size, blood pressure, cholesterol, weight, and medicines.

  • Choose balanced meals with vegetables, protein, fiber-rich carbohydrates, and fewer sugary drinks and refined foods.

  • Build toward at least 150 minutes of moderate activity weekly when medically appropriate.

  • If overweight, discuss a realistic weight-loss goal rather than using a restrictive crash diet.



Our guides to HbA1c and average glucose, normal fasting glucose, and blood sugar after eating explain these differences in more detail.




Important Safety Note


Arrange prompt medical testing if you develop excessive thirst, frequent urination, unexplained weight loss, recurrent infections, or repeated high glucose readings. Seek urgent care for vomiting, abdominal pain, difficult breathing, confusion, severe dehydration, high ketones, glucose above 400 mg/dL, or a meter displaying “HI.”





Doctor’s Note


Your fasting readings are reassuring, but the HbA1c of 6.0% should not be called normal. It is most consistent with prediabetes unless repeat testing shows that the result was affected by laboratory variation or a red-blood-cell condition. Confirm the result and use the findings to guide prevention—not fear.





Educational safety note: This answer is for general diabetes education only. It does not replace personal medical advice, diagnosis, or treatment. Do not start diabetes medicine, supplements, fasting, or a restrictive diet because of one HbA1c result without speaking with a healthcare professional.




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Last reviewed: July 2026.




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