Blood Sugar 138 mg/dl — Too High? Fasting & After Eating
Where 138 mg/dl sits — adjust to your situation
138 mg/dl as a fasting reading
Diabetes range
A fasting reading of 126 mg/dl or higher falls into the diabetes range. Diagnosis requires a repeat test on another day — take this result to your doctor.
Fasting = no food for at least 8 hours, typically first thing in the morning. More on fasting readings.
138 mg/dl after eating
Normal
Up to 139 mg/dl two hours after starting a meal is a normal response: your body is clearing glucose from the blood on schedule.
Guidelines measure 2 hours after the start of a meal. More on post-meal readings.
Pregnant with a fasting 138: call your care team today
During pregnancy, glucose targets are much tighter than at other times. The ADA goal for a fasting reading is under 95, and a fasting value of 92 or more on a glucose tolerance test already meets the criteria for gestational diabetes. A fasting 138 is far above both. It is also above 126, the level that in pregnancy points to overt diabetes, meaning diabetes that is likely to have been present before the pregnancy or that needs treating as such.
This is a reading to report the same day, by phone or through your clinic’s message system, not one to save for the next routine visit. It is not a reason for panic either. Raised glucose in pregnancy is common and very treatable, and acting promptly is what keeps the risks low for you and the baby.
Before you call: check the reading
A quick repeat helps the care team judge how fast to act:
- Wash your hands with soap and warm water and dry them well. Juice, fruit or lotion on the skin can raise a fingerstick sharply.
- Use a fresh test strip from a container that is not expired and has been kept closed.
- Recheck straight away. If the second value is also well above 95, report both.
Note when you last ate and drank. A true fasting value means at least eight hours without calories. If you had a snack in the night or juice before testing, the 138 is not a fasting result, but it is still worth mentioning, since after-meal targets in pregnancy are also strict: under 140 at one hour and under 120 at two hours.
What the care team is likely to do
Expect your team to arrange a lab glucose and often an A1C fairly quickly. If the high fasting level is confirmed, the usual next steps include:
- Regular home testing, typically fasting and after meals, with results reviewed every week or two.
- A visit with a dietitian or diabetes educator to plan meals that spread carbohydrate across the day.
- Medicine if needed. When diet and activity alone do not bring values to target, insulin is the medicine most often used in pregnancy, because it is well studied and does not cross into the baby’s blood in meaningful amounts.
- Extra monitoring of the baby’s growth with ultrasound later in pregnancy.
A fasting value this high early in pregnancy is often handled as diabetes that predated the pregnancy, which means closer follow-up and a check of glucose again after the birth.
Until you hear back
Keep eating regular meals; skipping food to bring numbers down is not safe in pregnancy and can cause ketones. Avoid sugary drinks and juice, which raise glucose fastest. Seek urgent care if you have heavy thirst with frequent urination, vomiting you cannot keep fluids down through, or you feel confused or very unwell. The how to test blood sugar page covers good fingerstick technique for the many checks ahead.
Measured right after exercise?
There is no official range for readings taken during or just after a workout, so the two classifications above do not apply to them. How exercise moves blood sugar.
How 138 mg/dl compares to a typical day
Typical day without diabetes; your reading is the horizontal line — within the range a normal day passes through; when you measured decides how it counts.
What to do with a reading of 138 mg/dl
Book a doctor's appointment to confirm with a lab test (fasting glucose or A1C). If you are already diagnosed, this reading belongs in your log for your care team.
What actually moves the number: How to lower blood sugar, Foods that steady your glucose and Exercise and blood sugar.
Save this reading
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Questions about 138 mg/dl
Is 138 mg/dl blood sugar normal?
It depends on when you measured. Fasting, 138 mg/dl is diabetes range (normal fasting range: 70–99 mg/dl). Two hours after a meal it is normal (normal post-meal range: 70–139 mg/dl).
What is 138 mg/dl in mmol/L?
138 mg/dl equals 7.7 mmol/L. Divide mg/dl by 18 to convert (used in the UK, Canada, Australia and most of Europe).
Does one reading of 138 mg/dl mean I have diabetes?
No single home reading is a diagnosis. Guidelines require a second abnormal lab result, either a different test from the same blood draw or a repeat on another day (fasting glucose, an oral tolerance test, or A1C). But a reading like this is exactly the reason those tests exist — take it to your doctor.
How accurate is a home reading of 138 mg/dl?
Home meters are allowed an error of ±15 mg/dl below 100 mg/dl and ±15 % from 100 up (ISO 15197), so a displayed 138 can correspond to a true value anywhere from 117 to 159 mg/dl. Fasting, that window crosses the 126 mg/dl line — a single home reading of 138 cannot settle which side you are truly on. That is a lab-test question, not a meter question. After a meal, the window touches the 140 mg/dl boundary.
What A1C would 138 mg/dl correspond to?
If 138 mg/dl were your average glucose over three months, it would work out to an A1C of about 6.4 % — in the prediabetes A1C range (5.7–6.4). A single reading is not an average — but the conversion shows what this level would mean as a habit. How the two measures relate: A1C and blood sugar.
I am not pregnant but planning to be. Does a fasting 138 matter now?
Yes. A fasting 138 is above the 126 diabetes threshold for anyone, and glucose control before conception matters for early pregnancy, when the baby’s organs form. See a doctor for lab tests before trying to conceive, so any treatment can start beforehand.
I already have gestational diabetes and woke up at 138. What should I do?
Report it to your team the same day. Your fasting target is under 95, so a single 138 suggests the overnight hours are not covered by your current plan. Teams often adjust bedtime snacks, meal timing or the evening insulin dose, but only they should make that change.
BloodSugarEasy — blood sugar reading report
Reading: 138 mg/dl (7.7 mmol/L)
Fasting classification: Diabetes range · After-meal classification: Normal
Reference: ADA criteria, reviewed 2026-11-03 · https://bloodsugareasy.com/blood-sugar-138/
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