Lab test4 min read
Random plasma glucose
Blood glucose measured at any time of day, even after eating and without fasting. It is useful when symptoms of diabetes are present.
According to MedlinePlus, the random blood glucose test can be done at any time, even after eating, needs no preparation, and is useful when diabetes is suspected because of symptoms. The NIDDK notes that it is used when there are symptoms of diabetes and the doctor does not want to wait.
The NIDDK and CDC state that a value of 200 mg/dL or higher indicates diabetes, and MedlinePlus (Blood sugar test page) adds that it is "possible diabetes" (11.1 mmol/L) and that a normal random value is usually 125 mg/dL or lower (6.9 mmol/L). According to the NIDDK and CDC, the diagnosis is usually confirmed with another test.
What is it?
According to MedlinePlus, it is a test that can be done at any time, even after eating, and requires no preparation.
According to the NIDDK, it does not require fasting and can be done at any time.
Why is it done?
According to the NIDDK, it is used when there are symptoms of diabetes and the doctor does not want to wait. MedlinePlus adds that it is useful because the results are immediate.
MedlinePlus notes that the test is also done when symptoms appear such as frequent urination, blurred vision and tiredness, or in confusion, fainting or seizures.
Preparation
It requires no special preparation and no fasting according to MedlinePlus and the NIDDK.
How is it done?
According to MedlinePlus, a blood sample is taken from a vein in the arm with a small needle into a tube, and you may feel a prick or mild pain.
Understanding the result
According to the NIDDK and CDC: 200 mg/dL or higher on a random test indicates diabetes (unit mg/dL). According to MedlinePlus this equals 11.1 mmol/L, and it notes that a normal random value is usually 125 mg/dL or lower (6.9 mmol/L). Laboratories and guidelines differ, so what counts is your laboratory's report and your doctor's interpretation.
According to the NIDDK and CDC, the diagnosis is usually confirmed with a second test, and a single number is not interpreted in isolation from symptoms and condition.
In the NIDDK table, no limit for normal or prediabetes is given for this test, only the diabetes limit.
Risks and side effects
According to MedlinePlus: the risks are very small: mild pain or a bruise at the needle site, and according to the Blood sugar test page, excessive bleeding, fainting, blood collecting under the skin or infection may occur.
Limits of the test
According to MedlinePlus (glucose tolerance test page), drugs, severe stress and strenuous exercise may affect the glucose level.
After the test
According to MedlinePlus: you and the doctor decide on the next tests; the NIDDK notes that the doctor usually uses a second test to confirm.
When do you need urgent help?
Call emergency services now 998
- According to the NIDDK, loss of consciousness or a seizure with low blood sugar is a dangerous condition needing immediate treatment, and someone who cannot treat themselves needs another person to call emergency services immediately.6
See your doctor within days
Educational content only — no diagnosis, and no substitute for a clinician.
Common questions
Questions for your doctor
- Do I need additional tests to confirm the result?
- Do my last meal or my medicines affect this reading?
- Which symptoms call for urgent review in my case?
References
- 1MedlinePlus / NLM. Blood Glucose Test. medlineplus.gov/lab-tests/blood-glucose-test/Health agencies & guidelines · Accessed 2026-10-07
- 2NIDDK / NIH. Diabetes Tests & Diagnosis. www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosisHealth agencies & guidelines · Accessed 2026-10-03
- 3MedlinePlus. Blood sugar test. medlineplus.gov/ency/article/003482.htmHealth agencies & guidelines · Accessed 2026-10-07
- 4CDC. Diabetes Testing. www.cdc.gov/diabetes/diabetes-testing/index.htmlHealth agencies & guidelines · Accessed 2026-10-07
- 5MedlinePlus. Glucose tolerance test - non-pregnant. medlineplus.gov/ency/article/003466.htmHealth agencies & guidelines · Accessed 2026-10-07
- 6NIDDK / NIH. Low blood glucose (hypoglycemia). www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/low-blood-glucose-hypoglycemiaHealth agencies & guidelines · Accessed 2026-10-05
- 7MedlinePlus / NLM. Hemoglobin A1C (HbA1c) Test. medlineplus.gov/lab-tests/hemoglobin-a1c-hba1c-test/Health agencies & guidelines · Accessed 2026-10-07
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Change log
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Educational content only — no diagnosis, and no substitute for a clinician.