Smoking and Blood Tests: How It Impacts Your Results
According to the CDC, 49.2 million US adults reported current tobacco product use, which is the equivalent of almost 20% of all adults. Because smoking is such a common occurrence, chances are, you’re a smoker as well.
Normally, your habit isn’t an issue (besides the obvious health effects it can have). However, you have a blood test coming up, and you can’t or won’t quit beforehand.
You want your test results to be accurate though, and you’re worried that your tobacco habit will affect the blood test accuracy. So will smoking before a blood test affect results? Read on to find out the answer to this question.
Will Smoking Before a Blood Test Affect Results?
First, we’ll tackle the question straight on. The answer is yes, smoking will affect your blood test results. This is because tobacco smoke contains thousands of chemicals, including:
- Nicotine
- Carbon monoxide
- Oxidizing agents
All of the above will alter your blood chemistry, as well as your cardiovascular system and metabolic functions.
Short-Term Effects of Smoking on Blood Tests
Now, there are two types of effects when it comes to smoking and blood tests. First, we’ll go over the short-term nicotine effects, which occur if you smoke a few hours before having your blood drawn.
As you may already know, you’ll have an increased heart rate when smoking. Your blood pressure increases too, and both of these things can affect cardiovascular markers.
In addition, you’ll have elevated levels of the following:
- Glucose levels: Nicotine triggers adrenaline, which then increases your blood sugar
- White blood cell count: Smoking activates the immune system
- Carboxyhemoglobin: This happens from inhaled carbon monoxide
Long-Term Effects of Smoking on Blood Tests
Not only can smoking have immediate and temporary changes to your blood chemistry, organ function, and disease markers, but chronic smoking can also lead to persistent alterations. Even if you stop smoking, these long-term effects can influence how your blood tests are interpreted for years to come.
Let’s delve into the long-term effects.
Chronic Inflammation and Immune Response
You may have chronically elevated white blood cell counts, as well as increased C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). As a result, doctors may investigate unnecessary causes of inflammation if they’re unaware of your smoking history.
Permanent Changes in Blood Vessels and Clotting
When you smoke long term, it can promote a pro-thrombotic (clot-prone) state. Damaged blood vessels can contribute to abnormal test results, so you may appear at a higher cardiovascular risk even after quitting.
Long-Term Impact on Lipid and Glucose Metabolism
Even with good diet and exercise habits, chronic smokers may often have persistently high LDL and low HDL. They may also have higher HbA1c and fasting glucose levels. This means that you may be flagged as prediabetic or at cardiovascular risk.
Altered Liver Enzyme Baselines
Chronic exposure to tobacco can induce liver enzymes (GGT and CYP450 enzymes) since your liver has to process tobacco-related toxins. This can mildly elevate your ALT or AST without actual liver disease, and this can mimic test results of those with fatty liver disease or alcohol-related liver damage.
Kidney Function and Blood Pressure Effects
Smoking can cause chronic hypertension, and this, in turn, can damage your kidneys. This can result in slightly elevated creatinine and blood urea nitrogen (BUN), as well as reduced glomerular filtration rate (GFR). The results can mimic early-stage kidney disease.
Persistent Hormonal Disruptions
Long-term smoking can lower testosterone levels in men and alter estrogen levels in women. In both, they can get increased cortisol levels. These results can misrepresent natural aging patterns or suggest you have imbalances caused by your lifestyle or stress.
Increased Risk of Cancer Markers Elevation
You probably already know that smoking is a major risk factor for several cancers, including lung, bladder, and pancreatic cancer. It can increase the chance of false positives or real elevations in tumor markers, such as:
- Carcinoembryonic antigen (CEA)
- CYFRA 21-1
- Neuron-specific enolase (NSE)
When this happens, it can lead to over-testing or early cancer screening.
Long-Term Respiratory and Oxygenation Impact
Often, smokers have chronic obstructive pulmonary disease (COPD), which alters their oxygen levels and carbon dioxide retention. This may cause abnormal results for blood gas analysis or oxygen saturation tests.
How Smoking Affects Specific Blood Tests
We’ve gone over short and long-term effects of smoking on blood tests, but this covers a broad spectrum. Below, we’ll go over specific blood tests and the effects of smoking you should be aware of:
- Complete blood count (CBC): elevated white blood cell count, elevated red blood cell count, elevated platelet count
- Lipid panel (cholesterol test): elevated total cholesterol, elevated LDL, lower HDL, elevated triglycerides
- Blood glucose and HbA1c: elevated blood glucose, elevated HbA1c
- Inflammatory markers: elevated CRP, elevated ESR
- Liver function tests: elevated ALT, AST, and GGT, affected bilirubin
- Coagulation panel: generally not affected significantly (PT, PTT, INR), but may have increased clotting tendencies
- Thyroid function tests: lowered TSH, slightly elevated T3/T4
- Kidney function tests: slightly higher creatinine, higher BUN
- Hormonal tests: elevated cortisol, altered sex hormone levels (estrogen and testosterone)
- Nicotine-specific tests: cotinine (up to 3-4 days)
How Long Should You Avoid Smoking Before a Blood Test?
For general medical testing, ideally, you should avoid smoking for 8-12 hours beforehand. If you’re having fasting tests (lipids, glucose), then you should refrain from smoking overnight or even longer. As for nicotine/cotinine testing, abstain for 3-4 days.
Do note that even one cigarette can affect certain test results. So if you want the most accurate results, avoid smoking completely for as long as possible.
Cease Smoking Before Your Blood Tests
The answer to the question, “Will smoking before a blood test affect results?” is “yes,” which means that you need to tell your healthcare provider that you smoke. This will help them interpret the results more accurately.
It’s best to quit smoking, as not only will this normalize most lab values, but it’ll also reduce your risk of misdiagnosis. Plus, it’ll be better for your health anyway. If quitting’s not possible, then at least avoid smoking the day of the test.
Get in touch with us today if you need blood testing services. Precision Labs customizes our services to every client to suit their personal needs.