Can this result diagnose a condition on its own?

No. Laboratory results are interpreted with symptoms, medical history, sampling conditions, and related tests.

Which reference range or cutoff should I use?

Start with the performing laboratory's report and the purpose of testing; diagnostic cutoffs are separate sourced clinical thresholds.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, symptomatic, or unexpected should be reviewed by a healthcare professional.

Information about a laboratory test

Fasting Blood Glucose: What Do the Numbers Mean?

Fasting blood glucose is plasma glucose measured after at least 8 hours without caloric intake and is a standard test used in diabetes/prediabetes diagnosis.

Test summary

Test name: Glucose
Abbreviations: GLU, FPG, FBS
Category: Endocrinology / Glucose Metabolism
Panel: Glucose Metabolism / Basic Metabolic Panel
Specimen: Plasma / serum
Common units: mg/dL, mmol/L

What does the test measure?

Measures the amount of glucose in the blood.

Why is the test ordered?

Used to screen for or diagnose diabetes/prediabetes, evaluate hypoglycemia, and monitor glucose control.

Information about a low result

A low result may occur with fasting, glucose-lowering medicines, or other clinical conditions; symptoms and timing matter.

Information about a high result

A high result may occur with diabetes/prediabetes, but illness, stress, and some medicines can also raise glucose.

Reference and clinical context

Use the performing laboratory's report and the sampling conditions first. Fasting status, timing, and whether the test is diagnostic or for monitoring can change interpretation.

Reference context 1

<= 99 mg/dL

Population: Nonpregnant adults
Pregnancy status: No
Specimen: Plasma

Normal fasting glucose context

The source uses <=99 mg/dL as the threshold for this context. Individual risk and laboratory context still matter.

Reference context 2

>= 100 – <= 125 mg/dL

Population: Nonpregnant adults
Pregnancy status: No
Specimen: Plasma

Prediabetes range

This sourced diagnostic threshold of >=100–<=125 mg/dL applies to nonpregnant testing; confirmation is usually required when classic symptoms are absent.

Reference context 3

>= 126 mg/dL

Population: Nonpregnant adults
Pregnancy status: No
Specimen: Plasma

Diabetes diagnostic threshold

This sourced diagnostic threshold of >=126 mg/dL applies to nonpregnant testing; confirmation is usually required when classic symptoms are absent.

Reference context 4

< 70 mg/dL

Population: People with diabetes
Specimen: Blood / plasma

Low-glucose threshold

For many people with diabetes, glucose <70 mg/dL is considered low; individual targets may differ.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

Fasting, random, and post-glucose-load results use different interpretation thresholds. Diagnostic results often require confirmation.

Related specialties

Endocrinology
Internal Medicine
Family Medicine
Pediatric Endocrinology

Frequently asked questions

Sources

Diabetes Tests & Diagnosis — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
U.S. government medical reference · 2026 · Fasting plasma glucose, A1C, OGTT, random glucose; diagnostic thresholds and pregnancy caveats · Verified: Aug 12, 2026
The A1C Test & Diabetes — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
U.S. government medical reference · 2026 · A1C meaning, diagnostic use, pregnancy and hemoglobin-related limitations · Verified: Aug 12, 2026
Low Blood Glucose (Hypoglycemia) — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
U.S. government medical reference · 2026 · Low-glucose context; <70 mg/dL threshold for many people with diabetes · Verified: Aug 12, 2026
Blood Glucose Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Blood glucose purpose, high/low context and related testing · Verified: Aug 12, 2026
Insulin in Blood — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Insulin blood testing and interpretation with glucose/C-peptide · Verified: Aug 12, 2026
C-Peptide Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · C-peptide use for endogenous insulin production and hypoglycemia context · Verified: Aug 12, 2026
The A1C Test & Race/Ethnicity — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
U.S. government medical reference · 2026 · Fructosamine as a shorter-term glycemic marker when A1C may be unreliable · Verified: Aug 12, 2026