Why is a vein usually chosen for blood tests?

I recently came across a post about blood collection:

Blood tests are an important means for doctors to assess our health conditions, and their importance is self-evident. Careful people may find that whether it is a routine physical examination or disease diagnosis, medical staff often draw blood from our veins rather than arteries. Veins, like the "tranquil river" of the human body, blood flows slowly in it with moderate pressure, making it a natural choice for blood draws. Arteries, on the other hand, are like turbulent waterfalls, with blood rushing through them and enormous pressure. Drawing blood from veins not only avoids the "turbulent torrents" of arteries, but also reduces the impact on the patient's heart and blood vessels, making the examination process more gentle and safe.

1. What is the difference between veins and arteries?

First, we need to know the difference between veins and arteries. Arteries are blood vessels that carry oxygen-rich and nutrient-rich blood from the heart to the entire body. They have high pressure, fast blood flow, thicker blood vessel walls, and are usually located deeper in the body. Veins, on the other hand, are blood vessels that carry used, less oxygenated blood back to the heart. They have low pressure, slow blood flow, thinner blood vessel walls, and are mostly located shallower on the surface of the body.

2. The vein is shallow and easy to operate

Veins are located relatively shallowly on the surface of the skin and are easy to find and puncture. For example, the veins on the inside of our elbows, the back of our hands, and the back of our feet are often clearly visible, allowing medical staff to complete the puncture quickly and accurately. In contrast, arteries are hidden deep under the skin, making them difficult to operate and requiring more professional skills and experience. For example, the radial artery is located in the wrist. Although it is sometimes used to draw blood, it is located deeper and the puncture is more difficult and risky.

3. Low venous pressure, safer

The pressure in the vein is lower than that in the artery, which makes it easier to stop bleeding after venous puncture. After the puncture is completed, just gently press for a while to effectively stop the bleeding and reduce the risk of bleeding. However, due to the high pressure in the artery, if the puncture is not done properly, it is easy to cause heavy bleeding, and even form a hematoma or pseudoaneurysm, which brings greater pain and risk to the patient. Therefore, drawing blood from the vein is not only simple to operate, but also can significantly reduce medical risks.

4. Venous blood can better reflect the body's metabolism

After flowing through various parts of the body, venous blood carries a wealth of metabolites and information, such as blood sugar, blood lipids, uric acid, etc., which can more truly reflect the body's metabolic status and organ function. In contrast, arterial blood has just been discharged from the heart, has a high oxygen content, and has less metabolic waste, making it difficult to fully reflect the actual situation of the body. Therefore, venous blood is more suitable for most routine blood tests.

5. Venipuncture is less painful and the wound heals quickly

Venous puncture is relatively less painful and the wound heals faster. Since the vein wall is thinner, the damage to the tissue is less during puncture, and the pain felt by the patient is also less. Arterial puncture is not only difficult and more painful, but also takes a long time to heal the wound, increasing the risk of infection. Therefore, from the perspective of patient comfort and recovery speed, venous blood drawing is a more ideal choice.

6. Arterial blood collection is required in special circumstances

Although venous blood drawing is the first choice in most cases, doctors will still choose to collect arterial blood in some special cases. For example, blood gas analysis requires measuring the content of gases such as oxygen and carbon dioxide in the blood. Since arterial blood has a high oxygen content, it is more suitable for blood gas analysis. In addition, for critically ill patients or patients with poor venous conditions, blood samples are sometimes collected from the arteries for emergency testing. Although arterial blood collection is difficult and risky, it is necessary in certain circumstances.

7. Precautions for blood drawing

When drawing blood from a vein, medical staff will take a series of measures to ensure the safety and accuracy of the operation. First, a tourniquet will be used above the puncture site to make the vein more visible and easier to puncture. Second, the puncture site will be strictly disinfected to prevent infection. During the puncture, the medical staff will insert the needle into the vein at an appropriate angle and quickly draw the required amount of blood. After the blood is drawn, the needle will be removed immediately and gauze or cotton balls will be pressed on the puncture site to stop the bleeding.

8. Patients’ cooperation and precautions

For patients, they also need to actively cooperate when doing blood tests. First, they should stay relaxed and avoid excessive tension that causes vasoconstriction and increases the difficulty of puncture. Secondly, they should make relevant preparations according to the doctor's advice before blood drawing, such as fasting, stopping medication, etc., to ensure the accuracy of the test results. After blood drawing, care should be taken to keep the puncture site clean and dry, and avoid strenuous exercise and heavy physical labor to promote wound healing. If any discomfort occurs during or after blood drawing, the medical staff should be informed in time and treated.

Therefore, veins are often chosen for blood tests, mainly because veins are superficial, easy to operate, safe, can reflect the body's metabolic status, cause less pain to the patient, and heal wounds quickly, etc. Although arterial blood is collected in special circumstances, venous blood collection is still the most common and important blood collection method in medical practice.