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A capillary sample is a blood sample collected by pricking the skin. Capillaries are tiny blood vessels near the surface of the skin.
Alternative NamesBlood sample - capillary; Fingerstick; Heelstick
How the test is performedSome blood tests are performed on blood obtained by pricking the skin of the finger, heel, or other areas and collecting a drop (or a few drops) of blood on a test strip or into a small container.
The area is cleansed with antiseptic and pricked with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How the test will feelSome people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performedBlood transports oxygen, food, waste products, and other materials within the body. It also helps regulate body temperature. Blood is made up of a fluid called plasma and cells. Plasma contains various dissolved substances. The cellular portion consists primarily of red blood cells, but also includes white blood cells and platelets.
Because blood has multiple functions, tests on the blood or its components can provide valuable clues in the diagnosis of a multitude of medical conditions.
Capillary blood sampling offers several advantages:
- It is relatively easy to obtain (it can be difficult to obtain blood from the veins, especially in infants).
- There are several collection sites on the body (heel, fingertips, etc.) and these can be rotated.
- Testing can be performed at home and with minimal training. For example, diabetics must check their blood sugar several times a day using capillary blood sampling.
There are some disadvantages to capillary blood sampling.
- Only a limited amount of blood can be obtained using this method.
- There are some risks associated with the procedure (see below).
- Capillary blood sampling may provide inaccurate results, such as falsely elevated sugar, electrolyte, and blood count values.
See the specific test.
What abnormal results meanResults vary depending on the test performed.
What the risks are- Excessive bleeding
- Fainting or feeling light-headed
- Infection (a slight risk any time the skin is broken)
- Scarring (occurs when there have been multiple punctures in the same area)
- Calcified nodules (sometimes occurs in infants, but usually disappear by 30 months of age)
- Damage to blood cells from this method of collection can sometimes cause inaccurate test results (and the need to repeat the test with blood drawn from a vein)
Capillary blood sampling is very useful when very small amounts of blood are needed or when blood is very difficult to obtain, such as in infants. Many times, however, when a larger sample is needed, the blood must be obtained from a vein.
ReferencesBabar T, Skugor M. Endocrinology. In: Carey WD, ed. Cleveland Clinic: Current Clinical Medicine 2010. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2010:section 4.
Lewandrowski K. Point-of-care testing: an overview and a look to the future. Clin Lab Med. 2009 Sep;29(3):421-32.
Hayrapetian-Dorsi L. Genetics. In: Custer JW, Rau RE, eds. Johns Hopkins: The Harriet Lane Handbook. 18th ed. Philadelphia, Pa: Elsevier Mosby; 2009:chap 13.
Reviewed ByReview Date: 05/01/2011
Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
What else can I help you with?
What are the essential steps for placing a solid sample in a capillary tube?
The essential steps for placing a solid sample in a capillary tube are: 1. Crush the solid sample into a fine powder. 2. Use a spatula to carefully transfer the powder into the capillary tube. 3. Use a tamper or glass rod to compact the sample down the length of the tube for accurate measurements.
What type of blood is used for a microhematocrit test?
For a microhematocrit test, capillary blood, usually obtained from a finger or heel stick, is used. The blood sample is placed into a special capillary tube and spun in a centrifuge to separate the components, allowing for measurement of the packed cell volume (hematocrit).
What is the advantage of using a plastic capillary tube when collecting blood?
Plastic capillary tubes are advantageous because they are disposable, reducing the risk of contamination between samples. They are also less fragile compared to glass capillary tubes, reducing the risk of breakage during sample collection and handling. Additionally, plastic capillary tubes are more cost-effective and easier to dispose of after use.
What steps can you take to determine the melting point of a substance that sublimes before it melts?
In such cases the melting point determination must be performed in a sealed capillary tube to avoid loss of sample. This can be achieved by heating the open end of the capillary tube, and with tweezers forcing it shut.
Why solvent is used in Paper chromatography?
Solvent is used in paper chromatography to carry the sample mixture along the paper and separate its components based on their affinity for the solvent and the paper. As the solvent moves through the paper, it dissolves the components of the sample and allows them to separate based on their solubility and interactions with the paper.
What is a capillary melting point?
The sample is placed in a sealed capillary and heated up to the melting.
What are the essential steps for placing a solid sample in a capillary tube?
The essential steps for placing a solid sample in a capillary tube are: 1. Crush the solid sample into a fine powder. 2. Use a spatula to carefully transfer the powder into the capillary tube. 3. Use a tamper or glass rod to compact the sample down the length of the tube for accurate measurements.
Why is it important to pack the sample tightly in the melting point capillary?
Packing the sample tightly in the melting point capillary ensures that the sample is in a uniform and compact shape, which leads to consistent and reliable melting point measurements. A tightly packed sample prevents air gaps or voids within the sample, which could affect the accuracy of the melting point determination.
Why should each sample be tightly packet in melting poin tinto the capillary tube prior to heating?
It is Important to pack tightly in order to prevent the entrance of air into the capillary tube.
How do they test the coagulation time of a blood sample?
Testing the coagulation time of a blood sample can be done in a few ways. The first is simply to record the amount of time it takes a sample to clot manually.
What type of blood is used for a microhematocrit test?
For a microhematocrit test, capillary blood, usually obtained from a finger or heel stick, is used. The blood sample is placed into a special capillary tube and spun in a centrifuge to separate the components, allowing for measurement of the packed cell volume (hematocrit).
What is the advantage of using a plastic capillary tube when collecting blood?
Plastic capillary tubes are advantageous because they are disposable, reducing the risk of contamination between samples. They are also less fragile compared to glass capillary tubes, reducing the risk of breakage during sample collection and handling. Additionally, plastic capillary tubes are more cost-effective and easier to dispose of after use.
What is capillary puncture?
Capillary puncture is a medical procedure where a small needle is used to collect a small amount of blood from the capillaries, typically in the finger or heel. This method is commonly used for blood glucose monitoring, hemoglobin testing, and other diagnostic tests where a small blood sample is sufficient.
What type of blood is used for microhematocrit test?
capillary blood
What is charging the chamber in a hemocytometer?
"Charging" simply means filling it with the sample. Pipette a small amount into the channel and allow it to be drawn up into the chamber by capillary action.
Which soil sample would lose water more?
The soil sample with smaller particles tends to hold water better than the soil sample with larger particles. This is because smaller particles have higher surface area and can retain more water due to capillary action. Therefore, the soil sample with larger particles would likely lose water more quickly.
What is another name for a test tube?
another name for test tube is culture tube or sample tube
