What does it mean if the blood drawn is dark purple?

Generally, blackish-purple blood during blood draw may be due to physiological phenomena or pathological causes such as acute nitrite poisoning or hyperlipidemia. The details are as follows:

I. Physiological Phenomenon

During venous blood collection, the oxygen content in veins is relatively low, which naturally results in darker-colored blood. This condition is usually not a cause for concern and represents a normal physiological phenomenon that typically does not require specific treatment.

II. Pathological Causes

1. Acute Nitrite Poisoning

This commonly occurs after consuming spoiled food or accidentally ingesting chemical substances, leading to methemoglobinemia in patients. Symptoms include cyanosis of the lips and blackish-purple blood during blood draw. Patients may also experience nausea, abdominal pain, and other symptoms. Immediate medical treatment is required, including administration of methylene blue injection or large doses of ascorbic acid.

2. Hyperlipidemia

This is usually caused by unhealthy dietary habits, resulting in lipoprotein metabolism disorders and increased blood viscosity. As a consequence, the color of the blood gradually changes. Patients can manage this condition by adjusting their diet and engaging in appropriate physical exercise.

In addition to the above factors, abnormal coagulation function, chronic obstructive pulmonary disease (COPD), and congenital heart disease may also contribute. If the underlying cause is unclear, patients should seek timely medical evaluation and treatment.