Glucose, Serum or Plasma (Concentration)
This test measures the amount of glucose (sugar) in your blood, either drawn from a vein or collected in a tube. It helps assess how well your body is using sugar for energy.
["Your blood sugar levels can tell doctors if you’re managing diabetes or other conditions affecting metabolism."]
Key facts at a glance
- LOINC
- 6749-6
- Short code
- Glucose 2.5h p 75 g Glc PO SerPl-mCnc
- Synonyms
- Glucose 2.5h p 75 g Glc PO SerPl-mCnc
- Category
- glucose
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 70
- Ref high
- 100
- Critical range
- 50 N/A – 400 N/A
- Fasting
- true
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82947
- SNOMED
- 260395008
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why It’s Done
Doctors order glucose tests to monitor blood sugar levels for conditions like diabetes, hypoglycemia (low blood sugar), or to check for metabolic issues. It may also be used during pregnancy, before surgeries, or to evaluate symptoms like excessive thirst, fatigue, or frequent urination.
What to Expect Before the Test
For a vein draw, you may need to fast (not eat or drink) for 8–12 hours before the test, depending on the reason. If you’re not fasting, you might drink water. For a fingerstick (if testing at home), eat and drink normally. Always follow your doctor’s instructions.
What Happens During the Test
A healthcare provider will insert a small needle into a vein in your arm or use a fingerstick to collect a blood sample. The process is quick and usually painless. If you’re fasting, the sample may be taken in a lab for precise measurement.
What the Results Mean
Results are reported as a concentration (e.g., milligrams per deciliter, mg/dL). High or low values may indicate diabetes, insulin resistance, or other metabolic disorders. Your doctor will interpret results in the context of your symptoms and medical history.
Reference range
Fasting: 70-100 mg/dLN/A
Fasting for 8-12 hours required. Water is permitted. Avoid chewing gum and smoking before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Glucose levels outside normal ranges can signal serious conditions. For example, persistently high levels may require diabetes management, while dangerously low levels can cause seizures or coma. Regular monitoring helps prevent long-term complications like nerve damage or heart disease.
Short name
Glucose Level
Frequently asked questions
What causes blood sugar to be too high?
What causes blood sugar to be too low?
How often should I get this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy