The health effects of smoking and what changes when you quit

Why you can feel ready for another cigarette so soon

Nicotine reaches your brain quickly. If you smoke regularly, your body gets used to it. As nicotine levels fall between cigarettes, you might feel restless or irritable. Lighting up again can take the edge off for a while. That temporary relief helps explain why a cigarette can feel calming even when the urge to smoke comes back soon after. ^[2]

How smoking affects your body over time

Lungs and airways. Cigarette smoke irritates your airways and makes it harder for them to clear mucus and particles you breathe in. Over time, smoking can lead to a persistent cough and raises your risk of COPD, a long-term lung disease that restricts airflow. With COPD, everyday tasks like climbing stairs can leave you short of breath. ^{[1, 3]}

Heart and blood vessels. Smoking damages the lining of your blood vessels, encourages plaque to build up and makes blood clots more likely. That can restrict blood flow and raise your risk of a heart attack or stroke. ^[4]

Cancer. Chemicals in cigarette smoke can damage DNA, which can contribute to cancer. Smoking raises the risk of lung cancer as well as several other cancers, including cancers of the mouth, throat and bladder. ^{[1, 5]}

Is one cigarette a day harmful?

Yes. People who regularly smoke one cigarette a day have a higher risk of coronary heart disease and stroke than people who have never smoked. For your heart and blood vessels, the risk remains higher than you might expect from such a small number of cigarettes. If you’re cutting back, that can be a step toward quitting altogether. ^[6]

How secondhand smoke affects the people around you

People can breathe in harmful chemicals from both a burning cigarette and the smoke someone breathes out. Secondhand smoke raises the risk of heart disease, stroke and lung cancer in adults. In children, it can contribute to respiratory infections and trigger asthma attacks. ^{[7, 8]}

The World Health Organization estimates that secondhand smoke causes more than 1.6 million deaths worldwide each year. ^[12] Keeping your home and car smoke-free helps protect the people who share those spaces with you.

How does smoking affect pregnancy?

Smoking during pregnancy can reduce the amount of oxygen your baby gets and interfere with lung development before birth. It also makes it more likely that your baby will be born early or have a low birth weight. ^{[8, 9, 10]}

Quitting can help even if you’re already pregnant. If you’re finding it hard to stop, your midwife or doctor can help you find support. ^[10]

What can improve after you quit?

In the first few days after your last cigarette, carbon monoxide levels in your blood fall. Over the following months, you may cough less and find it easier to breathe. Your risk of a heart attack, stroke and several cancers also drops over time. Those benefits still apply if you’ve smoked for years. ^[11]

Curious about what changes first? See the quit-smoking timeline. If you’re thinking about quitting, the step-by-step quit guide can help you get ready for your first smoke-free day.