On March 24, well-known education blogger Zhang Xuefeng died of sudden cardiac death. Previously, some netizens reminded him that "purple lips may indicate a bad heart. It is recommended to get checked as soon as possible." This association is not uncommon, and similar discussions often appear on the Internet. So what exactly is going on with purple lips? Does it really mean that your heart is bad?
Why do lips turn purple?
When brushing their teeth at night, someone will suddenly stop in front of the mirror - their lips under the light seem a little darker than usual, even faintly purple. Such moments often bring about a direct association: Is there something wrong with the heart?
But from a medical point of view, purple lips are more of a hint than a definite answer. Not all dark or purple lips mean abnormality.
Source: Internet
The reason why lips are easy to observe is because the skin here is thin and rich in blood vessels.
When the deoxygenated hemoglobin in the blood increases to a certain level, the local area will appear blue-purple. This phenomenon is medically called cyanosis. Usually, when the concentration of reduced hemoglobin in the blood reaches above about 5.0g/dL, this change can only be detected by the naked eye [1].
Further tracing its origin, we will find that purpleness is actually the result of the participation of multiple systems: the lungs are responsible for gas exchange. Once there is a problem with ventilation or ventilation, blood oxygen levels will drop; the heart is responsible for circulation. If the structure or function is abnormal, insufficiently oxygenated blood may enter the systemic circulation; and if the blood itself is abnormal, it will also affect the ability to transport and release oxygen [2].
Therefore, simply attributing blue lips to a bad heart often ignores the more complete physiological background.
Before judging abnormalities, we need to clarify a more basic question - what is considered a normal lip color?
In fact, there is no uniform standard for our lip color itself. A study of 514 women showed that there are obvious individual differences in natural lip color, and 53 different lip color types could be summarized [3]. There is a lot of overlap between different people, and there is no one absolutely uniform standard color.
Reference [3]: Lower lip color measurement results of 514 subjects
Because of this, some people are redder, some are darker, and some have a slightly purple tint. These differences in themselves do not point to health problems.
In practical judgment, what is more important than the shade of color is whether it has changed. Long-term stable lip color is usually of little significance; obvious changes in a short period of time are more worthy of attention. This way of observation, which shifts from "static color" to "dynamic change", is often closer to the logic of medical judgment.
How to tell if your lips are purple from the cold or are truly cyanotic?
In winter or in an air-conditioned environment, many people will temporarily experience purple lips, but they will return to normal soon. This situation is mostly related to peripheral vascular reactions.
Cold stimulation can cause vasoconstriction, slow down local blood flow and increase oxygen utilization, resulting in temporary color changes. This type of peripheral cyanosis usually does not involve the oral mucosa, the tongue color remains normal, and it can recover after keeping warm [1].
In contrast, central cyanosis involves systemic oxygenation problems. At this time, not only the lips will turn purple, but the tongue and oral mucosa will also change color simultaneously, which often persists and is not easy to resolve on its own [1].
In real life, the distinction between the two is not complicated: whether there is a clear trigger, whether it can be recovered, and whether the oral mucosa is involved, often provide key clues.
Furthermore, in some conditions related to vascular function, such as acrocyanosis, cold can induce symmetrical purple discoloration that is usually painless and not accompanied by general discomfort [4]. These situations further suggest that color change itself needs to be understood in a specific context.
If you turn your perspective to infants and young children, the situation is different.
In China, about 150,000 newborns are affected by congenital heart disease every year, and about one-third of them are of the type that require early intervention [5]. Some of these children develop persistent cyanosis early in life.
It is worth noting that even under the screening system, about 0.07% of screen-negative infants are subsequently diagnosed with congenital heart disease [5]. In other words, preliminary screening results cannot completely replace subsequent observations.
Therefore, in infants and young children, if persistent cyanosis of the lips occurs, especially if it is accompanied by difficulty feeding, worsening when crying, or poor weight gain, early medical evaluation should be conducted.
When the problem is not with the heart and lungs, the blood may also be involved
Sometimes, cyanosis persists even if heart and lung tests show no abnormalities. In this case, blood factors need to be further considered.
For example, methemoglobinemia will change the structure of hemoglobin, affecting its ability to release oxygen normally. In one case report, a 49-day-old infant developed significant cyanosis, with a methemoglobin ratio of 44.7% and a special color in the blood. However, routine oxygen inhalation did not improve significantly [6].
This type of situation suggests that purple discoloration is not always "insufficient oxygen supply", but may also involve changes in the "oxygen carrying and oxygen releasing mechanism". Understanding this helps avoid simplistic judgments.
How to tell if something is wrong with your body?
In the home environment, most people do not have the ability to make medical judgments, so there is no need to try to "guess the disease" by color.
A more practical way is to observe several key issues:
Whether the change is new or ongoing;
Are there any clear triggers, such as cold or mood changes?
Ability to recover after rest or warmth;
Is it accompanied by shortness of breath, chest tightness, fatigue, etc.;
For infants and young children, it is also necessary to pay attention to the feeding situation and growth status.
When conditions permit, a finger-clip oximeter can be used as an auxiliary tool. Although there is a certain error, it has more reference significance than judging by the naked eye [7]. If blood oxygen continues to be low or is accompanied by obvious discomfort, you should seek medical evaluation in time.
As I said at the beginning, the color of your lips is more of a hint. What really needs to be paid attention to are the changes behind it and other signals that the body is sending.
References
[1]Pahal P, Goyal A. Central and Peripheral Cyanosis. [Updated 2022 Oct 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559167/
[2]Wang L, Ye Y, Li D, et al. Clinical presentations of cyanosis associated with acquired methemoglobinemia in infants. Front Pediatr. 2025;13:1563277.
[3]Charton Z, Vergnaud H, Caisey L, et al. Development of a lip color chart across four ethnicities. Int J Cosmet Sci. 2026;48:161–171.
[4]Demirciog?lu D, O¨ztu¨rk Durmaz E. Acrocyanosis: The Least Known Acrosyndrome Revisited. Dermatol Res Pract. 2025;2025:2904301.
[5]Tian Y, Gu Q, Hu X, et al. Newborn Screening for Congenital Heart Disease: A Five-Year Study in Shanghai. Int J Neonatal Screen. 2025;11:38.
[6]Wang L, Ye Y, Li D, et al. Case Report: Clinical presentations of cyanosis associated with acquired methemoglobinemia in infants. Front Pediatr. 2025;13:1563277.
[7]Fair FJ, Furness A, Higginbottom G, et al. Systematic review of Apgar scores & cyanosis in Black, Asian, and ethnic minority infants. Pediatr Res. 2025;97:939–952.
Planning and production
Author丨Jiang Yongyuan, Master of Internal Medicine, Third Military Medical University
Review | Ma Fangfang, deputy chief physician and associate professor of the Department of Cardiovascular Medicine, First Hospital of Hebei Medical University
Planning丨Zhang Linlin
Editor in charge丨Wang Mengru
Review | Xu Lai Zhang Linlin