Glucose
Measures blood sugar, usually after a fast. Screens for prediabetes and diabetes and checks whether a single draw matches how you actually fasted.
Glucose is the fuel your cells run on right now, and your bloodstream only holds a small slice at any moment. A fasting draw asks what that slice looks like after your insulin system had a quiet night without food. High fasting glucose can mean prediabetes, diabetes, stress hormones, poor sleep, or a fast that was not really a fast. Low fasting glucose is less common but can track with too much diabetes medicine, unusual insulin patterns, or other hormone issues. Doctors pair this number with A1c, symptoms, and sometimes a repeat test because one morning does not define a decade.
Self-Pay Price Comparison
| Provider | Price | vs. Highest | Order |
|---|---|---|---|
Quest QuestHealth self-pay | Not Available | N/A | Check Provider Site · Quest |
LabCorp Labcorp OnDemand | $39.00 | Highest | Order · LabCorp |
GoodLabs Discount lab network | $8.00Best value | Best price | Order · GoodLabs |
What This Test Measures
This order returns one blood glucose concentration, almost always after fasting when the requisition says fasting glucose. Here is what that line reflects:
Sugar dissolved in plasma at draw time; high after eating or with prediabetes and diabetes, high while fasting points toward impaired fasting glucose or diabetes when the fast was real, low can mean too much insulin or medicine, a missed meal, or an over-corrected reading.
How to Read Your Results
Fasting glucose is a snapshot; A1c is the rolling average. Here is how to read the three common result shapes without overfitting one draw:
| Marker | Normal Range | If Flagged | What It Might Mean |
|---|---|---|---|
| Fasting glucose (high) | MedlinePlus blood glucose overview: fasting plasma glucose below 100 mg/dL is often cited as a usual adult target band; 100-125 mg/dL fits many prediabetes conversations; 126 mg/dL or higher on repeat testing is the classic diabetes threshold range used in guidelines. | high | Stress, illness, steroid medicines, bad sleep, or a weak fast can bump a single draw. Your doctor often repeats the test or adds A1c before locking a label. |
| Fasting glucose (low) | Below about 70 mg/dL, many clinicians treat symptoms of low sugar as hypoglycemia even when you feel fine. | low | Medicines, alcohol, missed meals, and rare hormone tumors can drop glucose. Recurrent lows need a structured workup, not guesswork from one value. |
| Fasting glucose (borderline with normal A1c) | A1c describes roughly three months; fasting glucose is one morning. They can disagree when recent weeks do not match that morning. | abnormal | Conflicting numbers are when clinicians repeat labs, review meters, or order oral glucose tolerance testing instead of picking a favorite line. |
When to Order
Prediabetes or diabetes screening age
Many adults add fasting glucose on the same schedule as lipids when risk factors stack.
Symptoms of high or low sugar
Thirst, frequent urination, blurry vision, or shakiness and sweating all push doctors toward glucose plus A1c.
PCOS, fatty liver, or metabolic syndrome workup
Fasting glucose joins lipids and sometimes insulin to describe how hard the body is working to control sugar.
Starting or adjusting diabetes medicines
Fasting glucose helps judge morning control; it is not the only line on the report.
Pregnancy planning or gestational follow-up
OB teams use glucose challenges and fasting rules that differ from a routine adult screen; follow the order they wrote.
Prep & Logistics
- Fasting
- Fasting may be required
- Sample
- Blood draw after the fast your lab specifies (often 8 hours, water rules vary)
- Results
- Usually 24-48 hours; many portals update the same day or the next.
- Referral
- Often self-order (check local rules)
- Markers
- Fasting plasma or serum glucose (mg/dL or mmol/L per report). Random glucose is a different order; confirm the label on your requisition.
Tests That Pair With This One
Three-month glucose average when fasting glucose is borderline or diabetes risk is the whole point of the visit.
Fasting insulin with fasting glucose when insulin resistance or PCOS is on the differential.
Kidney function and electrolytes when diabetes medicines or dehydration could skew the glucose story.
Heart risk overlay when metabolic syndrome is why glucose entered the chart.
FAQ
One high fasting glucose—do I have diabetes?
Not from one draw. Stress, poor sleep, a borderline fast, or illness can bump a single value. Repeat testing, A1c, and sometimes glucose tolerance testing settle the label—your clinician sets the sequence.
I had a cough drop before the draw. Does that break the fast?
Sugar in the mouth can matter. Tell the phlebotomist and your doctor; you may need a repeat when the fast was clean.
My glucose was high but A1c was normal. Which wins?
Neither wins alone. A1c is a longer window; fasting glucose is one morning. Your doctor may repeat both, check home meters, or look for stress and illness timing.
Is this the same as a finger-stick at the pharmacy?
Same molecule, different context. Lab plasma glucose follows a controlled fast and calibration; finger-sticks vary with technique and strips. Use both only how your doctor asks.
Sources
Prices pulled directly from provider websites and verified by hand. Reference context from MedlinePlus where linked. Not generated by AI.
- GoodLabs - product page (pricing context)(verified 2026-03-23)
- LabCorp OnDemand - fasting glucose test (pricing context)(verified 2026-03-23)
- MedlinePlus - Blood Glucose Test overview
- Clinical context: LabRecon editorial team. Not medical advice. For informational use only.
Fasting serum glucose quantification. Primary screen for diabetes, prediabetes, and hypoglycemia. Results must be interpreted in the context of fasting status.