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How is genetic testing done?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Testing

How is genetic testing done?

Genetic testing is performed by analyzing biological samples in a laboratory to identify specific changes in chromosomes, DNA, or proteins.

Overview

Once a person decides to proceed with genetic testing, a health care provider can arrange the process, often as part of a genetic consultation. Before testing, it is important to understand the procedure, the benefits and limitations, and the possible consequences of the results. This process of education and obtaining permission is known as informed consent.

Sample Collection

Genetic tests are performed on various biological samples, including:

  • Blood
  • Hair
  • Skin
  • Amniotic fluid (the fluid surrounding a fetus during pregnancy)
  • Other tissue

A procedure called a buccal smear uses a small brush or cotton swab to collect cells from the inside surface of the cheek. Once collected, the sample is sent to a laboratory where technicians analyze it for specific changes in chromosomes, DNA, or proteins, depending on the suspected disorder. Results are reported in writing to the patient's doctor, genetic counselor, or directly to the patient if requested.

Newborn Screening

Newborn screening tests are conducted using a small blood sample taken by pricking the baby's heel. Unlike other forms of genetic testing, parents typically only receive the result if it is positive. If a result is positive, additional testing is required to determine if the baby has a genetic disorder.

Direct-to-Consumer Testing

Individuals may also obtain genetic testing directly from a testing company without going through a health care provider. Those who receive positive results or are found to be at higher risk for a disorder through this method are encouraged to follow up with a genetic counselor or other health care provider.

Frequently Asked Questions

The turnaround time varies by test type and laboratory workload. Simple genetic panels may take 1–2 weeks, while more complex sequencing or newborn screening results can take 3–4 weeks or longer. Your provider can give you an estimate based on the specific test ordered.
Newborn screening uses a heel‑stick blood sample taken within the first few days of life. The test screens for a panel of metabolic and genetic disorders. Parents usually receive a report only if a positive result is found, after which confirmatory testing is performed. Unlike other tests, newborn screening is mandatory and aimed at early detection to prevent serious health problems.
Schedule a follow‑up appointment with a genetic counselor or your primary care provider. They can order a confirmatory, CLIA‑certified test and help interpret the result in the context of your health history and family background.///
Common samples include blood drawn by a phlebotomist, saliva collected with a swab or oral rinse, hair follicles, skin biopsy, or amniotic fluid during pregnancy. For a buccal smear, a healthcare provider uses a small brush or cotton swab to gently scrape cells from the inside of the cheek. Each sample type is chosen based on the specific test and the patient’s situation.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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