The essentials

Without diabetes, blood sugar is usually 70 to 99 mg/dL (3.9 to 5.5 mmol/L) after an overnight fast and below 140 mg/dL (7.8 mmol/L) two hours after eating[1][7]. These lines barely move with age; diabetes and pregnancy change the targets, not the definition of normal[2][10].

How do you read blood sugar on a lab report?

Fictitious example of a lab report (United States format)
TestResultReference rangeFlag
Glucose, fasting (plasma)108 mg/dL70–99 mg/dLH ↑
Hemoglobin A1c5.6 %<5.7 %None
Estimated average glucose (eAG)114 mg/dLNot setNone
  1. Glucose, fasting: sugar in plasma from a vein, after at least 8 hours without calories[1].
  2. Result and range: 108 mg/dL falls in the prediabetes band (100 to 125), if you truly fasted; one value needs a repeat[1].
  3. Hemoglobin A1c: a three-month average with its own cut-offs (see our HbA1c results guide).
  4. eAG: the A1c expressed in mg/dL; 5.6% gives about 114[11].
  5. Flag: "H" means above the lab's range, not a diagnosis.

A glucose line rarely comes alone. BloodSense explains every line of your lab report in plain words.

Understand your lab results

What does a blood sugar number measure?

Blood sugar (glucose) rises after a meal and insulin brings it down within a few hours, so "normal" depends on timing: fasting (8 hours, water only), random (any time), 1 to 2 hours after a meal, or 2 hours after a 75 g glucose drink in a lab[1][2]. Our guide to fasting blood sugar results covers the fasting test in depth.

Labs test plasma from a vein; a meter uses a fingertip drop, and a sensor (CGM) reads fluid under the skin, which can lag when sugar moves fast[6]. Home devices track; diagnosis rests on lab tests[1].

What are normal blood sugar levels?

US numbers for adults without diabetes, with the prediabetes and diabetes lines[1][7]:

Normal blood sugar levels chart, adults without diabetes
Moment of the testNormalPrediabetesDiabetes rangeSource
Fasting (8 hours or more)70–99 mg/dL (3.9–5.5 mmol/L)100–125 mg/dL (5.6–6.9 mmol/L)126 mg/dL or more (7.0 mmol/L)ADA, CDC[1][7]
2 hours after 75 g glucose drinkBelow 140 mg/dL (7.8 mmol/L)140–199 mg/dL (7.8–11.0 mmol/L)200 mg/dL or more (11.1 mmol/L)ADA, CDC[1][7]
Random (any time)No official range; usually below 140 mg/dLNot defined200 mg/dL or more (11.1 mmol/L) with symptomsADA, CGM study[1][10]
HbA1c (3-month average)Below 5.7% (39 mmol/mol)5.7–6.4% (39–47 mmol/mol)6.5% or more (48 mmol/mol)ADA, CDC[1][7]
Low at any timeBelow 70 mg/dL (3.9 mmol/L); below 54 mg/dL (3.0 mmol/L) is clinically importantADA[2]

In a study of 153 healthy children and adults wearing a sensor for up to 10 days, sugar stayed between 70 and 140 mg/dL about 96% of the time, with a median of 30 minutes a day above 140[10].

Your lab's range comes first. Read your result against the range printed next to it.

What are the targets if you have diabetes?

Targets are goals agreed with your care team, not normal values[2].

Usual blood sugar targets for nonpregnant adults with diabetes
MeasureUsual targetSource
Before meals80–130 mg/dL (4.4–7.2 mmol/L)ADA[2]
1 to 2 hours after the start of a mealBelow 180 mg/dL (10.0 mmol/L)ADA[2]
HbA1cBelow 7.0% (53 mmol/mol) for many adultsADA[2]

What is a normal blood sugar level by age?

Without diabetes, US guidelines use the same lines from childhood to old age[1]. Sensor averages were 98 to 99 mg/dL in every age group from 7 years, and 104 mg/dL over 60[10]. Age charts online mostly show diabetes treatment targets.

Blood sugar by age group: normal values and diabetes targets
Age groupWithout diabetesWith diabetes: usual targetsSource
Children and teensAdult lines: fasting below 100 mg/dL, A1c below 5.7%A1c below 7% for most; below 6.5% if safe, and for most with type 2ADA[1][4]
Adults 18 to 64Fasting 70–99 mg/dL; below 140 mg/dL 2 hours after eatingBefore meals 80–130; after meals below 180 mg/dL; A1c below 7%ADA[1][2]
Older adults, good healthSame lines; averages slightly higherA1c below 7.0–7.5%; fasting 80–130; bedtime 80–180 mg/dLADA[3][10]
Older adults, several illnessesSame linesA1c below 8.0%; fasting 90–150; bedtime 100–180 mg/dLADA[3]
Older adults, very poor healthSame linesA1c not relied on; fasting 100–180; bedtime 110–200 mg/dLADA[3]

Looser goals in frail older adults are about safety: a fall from low sugar can do more harm than a higher number[3].

What blood sugar is normal in pregnancy?

The lines are tighter. Between 24 and 28 weeks, a 75 g glucose test points to gestational diabetes if any value reaches 92 mg/dL fasting, 180 at 1 hour or 153 at 2 hours[1]. With diabetes in pregnancy, usual goals are below 95 mg/dL (5.3 mmol/L) fasting and below 140 at 1 hour or 120 at 2 hours after meals, with an A1c ideally below 6% without lows[5].

How do you convert mg/dL to mmol/L?

Divide mg/dL by 18, the unit used in most of Europe, Canada and Australia: 54 = 3.0, 70 = 3.9, 100 = 5.6, 126 = 7.0, 140 = 7.8, 180 = 10.0 and 200 = 11.1 mmol/L.

What makes blood sugar too high or too low?

For warning signs and what to do now, see high and low blood sugar symptoms. On a lab report:

  • Common Not truly fasting: sweetened coffee or a late snack pushes a "fasting" value up[1].
  • Common Prediabetes or type 2 diabetes, often with insulin resistance (HOMA-IR)[1].
  • Possible Stress from an illness, surgery, infection or injury, and steroid medicines, including a steroid shot into a joint[9].
  • Possible Lows with insulin or some diabetes pills, after a missed meal or extra exercise[2].
  • Rare A falsely low lab value: cells keep using sugar if the sample waits too long[1].
  • Rare Type 1 diabetes in a child or young adult; a C-peptide test can help sort out the type[1].

What can make a blood sugar reading wrong?

A home meter counts as accurate when 95% of readings fall within 15% of the lab value[6]: for a lab 100 mg/dL, 87 or 113 is still fine. Check:

  • At least 8 hours with water only (see fasting before a blood test)[1].
  • Hands washed and dried before a finger-prick[12].
  • Strips in date, stored as directed, vial closed; a control test with each new box[12].
  • Fingertip, not forearm, when sugar may be changing, such as after meals or exercise[12].
  • Very high or low hematocrit, vitamin C or acetaminophen can skew some meters[6].
  • Your meter compared with a lab result at your next blood test[12].

When is a blood sugar level dangerous?

When to see a doctor

  • Emergency: call 911 if someone with low sugar passes out, has a seizure or has received glucagon[15], or if high sugar comes with fruity breath, trouble breathing, vomiting that stops you keeping liquids down, or stays at 300 mg/dL or above[8].
  • Within 24 to 48 hours for a first fasting result of 126 mg/dL or more, a reading of 200 mg/dL or more with thirst and frequent urination, or repeated lows below 70 mg/dL[1][2]. If you are at risk of ketoacidosis, check ketones when sugar is above 200 mg/dL and you feel unwell[2].
  • At your next appointment for a fasting value of 100 to 125 mg/dL, an A1c of 5.7 to 6.4%, or home readings that often miss your targets[1].

Questions to ask your doctor

  1. Was my sample taken fasting, and does my result need a repeat test?
  2. Which blood sugar targets fit my age and health?
  3. Should I check my sugar at home, and when?
  4. Do I need an A1c or a fructosamine test as well?

What else do people ask about blood sugar charts?

Is 13.1 mmol/L blood sugar high?

Yes. 13.1 mmol/L is about 236 mg/dL, above normal at any time and above the usual diabetes targets. Call your care team if it repeats.

Does stress affect blood sugar?

Yes. The stress of an illness, surgery or injury can raise blood sugar for a while; it usually returns to normal once the stress has passed.

What is a good average blood sugar?

Without diabetes, sensor averages are close to 100 mg/dL. With diabetes, an A1c of 7% equals an estimated average of about 154 mg/dL.

Where do these numbers come from?

  1. American Diabetes Association. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S27-S49. doi:10.2337/dc26-S002 (accessed October 25, 2026)
  2. American Diabetes Association. 6. Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S132-S149. doi:10.2337/dc26-S006 (accessed October 25, 2026)
  3. American Diabetes Association. 13. Older Adults: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S277-S296. doi:10.2337/dc26-S013 (accessed October 25, 2026)
  4. American Diabetes Association. 14. Children and Adolescents: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S297-S320. doi:10.2337/dc26-S014 (accessed October 25, 2026)
  5. American Diabetes Association. 15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S321-S338. doi:10.2337/dc26-S015 (accessed October 25, 2026)
  6. American Diabetes Association. 7. Diabetes Technology: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S150-S165. doi:10.2337/dc26-S007 (accessed October 25, 2026)
  7. Centers for Disease Control and Prevention. Diabetes Testing. cdc.gov (accessed October 25, 2026)
  8. Centers for Disease Control and Prevention. Diabetic Ketoacidosis. cdc.gov (accessed October 25, 2026)
  9. MedlinePlus, National Library of Medicine. High blood sugar. medlineplus.gov (accessed October 25, 2026)
  10. Shah VN, DuBose SN, Li Z, et al. Continuous Glucose Monitoring Profiles in Healthy Nondiabetic Participants: A Multicenter Prospective Study. J Clin Endocrinol Metab. 2019;104(10):4356-4364. doi:10.1210/jc.2018-02763 (accessed October 25, 2026)
  11. Nathan DM, Kuenen J, Borg R, et al. Translating the A1C Assay Into Estimated Average Glucose Values. Diabetes Care. 2008;31(8):1473-1478. doi:10.2337/dc08-0545 (accessed October 25, 2026)
  12. US Food and Drug Administration. Blood Glucose Monitoring Devices. fda.gov (accessed October 25, 2026)
  13. US Preventive Services Task Force. Prediabetes and Type 2 Diabetes: Screening. 2021. uspreventiveservicestaskforce.org (accessed October 25, 2026)
  14. Medicare.gov. Diabetes screenings. medicare.gov (accessed October 25, 2026)
  15. National Institute of Diabetes and Digestive and Kidney Diseases. Low Blood Glucose (Hypoglycemia). niddk.nih.gov (accessed October 25, 2026)

General health information only. It does not replace advice from a clinician who knows your history.