#299 The 10 Most Important Atrial Fibrillation Lab Tests: How to Optimize Your Biomarkers

The 10 Most Important Atrial Fibrillation Lab Tests

No one wants to suffer from heart failure, strokes, or premature death from atrial fibrillation.  Wouldn’t it be great if there were a few simple lab tests your doctor could order that would allow you to put your atrial fibrillation into remission?  In this article, I discuss the ten most important atrial fibrillation lab tests.

1.  C-Reactive Protein (CRP)

Of all the blood tests your doctor could order for atrial fibrillation, C-Reactive protein (CRP) is probably the simplest and most overlooked.  The reason why this test is so important is that it gives you a general sense of how much unnecessary inflammation is going on in your body.  And unless you are fighting off a cold or other illness, it is pretty accurate.

Years ago we published a study showing that CRP was a powerful predictor of who would get atrial fibrillation.  The reason for this is that unnecessary inflammation is associated with scarring in the heart.  And the more scarred up the heart is the more likely you will have disrupted electrical pathways with the end result of atrial fibrillation.

CRP is also a marker of left atrial enlargement.  And the left atrium of the heart is where most cases of atrial fibrillation originate.  Interestingly, CRP has been shown to go down over time with a successful atrial fibrillation ablation procedure.

If your CRP isn’t below 1.0 mg/L then you have some work to do to decrease your atrial fibrillation risk.  The single best thing you can do to lower your CRP is to get your waist size down to 35 inches (90 cm) if you’re a man and 32 inches (81 cm) for women.  The reason for this is that atrial fibrillation risk tracks waist size and waist size tracks visceral fat.

Visceral fat, especially fat surrounding the heart, releases cytokines which fire up intense inflammation.  Other ways to reduce unnecessary inflammation in your heart are to optimize your diet, daily exercise, sleep, and stress levels.  In rare cases, atrial fibrillation may be driven from chronic infections or other inflammatory reactions such as H. pylori infections in the gastrointestinal system, excessive mouth bacteria, or even a “leaky gut.”

2. Hemoglobin A1C

Along with CRP, hemoglobin A1C is another often neglected lab test for atrial fibrillation patients.  Indeed, it is unusual for me to see an atrial fibrillation patient with a CRP below 1.0 and a hemoglobin A1C below 5.7.

The hemoglobin A1C test simply measures how much glucose in your blood has been sticking to your red blood cells over the last two to three months. Obviously, the lower your average blood glucose the less of a sugar coating your red blood cells will have.  From a definition standpoint, a hemoglobin A1C of 5.7 indicates prediabetes and a level of 6.5 means full-blown diabetes.

Depending on which study you look at, diabetes increases your risk of atrial fibrillation by about 50%.  Other studies show that the higher your hemoglobin A1C, or the longer you have had diabetes, the more likely you are to also suffer from atrial fibrillation.  The reason why high blood glucose may damage the electrical system of the heart isn’t entirely clear but recent research suggests that blood glucose fluctuations may cause cardiac scarring through reactive oxygen species from upregulation of the Txnip protein.

If your hemoglobin A1C isn’t below 5.7, its time to get busy.  The single best way to get your hemoglobin A1C back to normal is to shoot for a waist size of 35 inches for men and 32 inches for women.  Additional strategies include religious daily exercise, no sugar, no flour, and no eating after 7 PM at night.

3. Thyroid Panel

Thyroid disease, especially from an overactive thyroid (hyperthyroidism), and atrial fibrillation go hand in hand.  Even our former US president, George Herbert Walker Bush, was struck with atrial fibrillation from hyperthyroidism while serving as president.

In my experience, at least 1% of my atrial fibrillation patients got there from an overactive thyroid.  Fortunately, this is something that is easily corrected.

Excessive thyroid hormone is a very potent stimulant.  So, just like any other stimulant, the more thyroid hormone you have the higher your risk of atrial fibrillation.  And it doesn’t matter if it is T3 or T4 that is elevated.  Indeed, any thyroid hormone elevation increases risk.  Even people with thyroid hormone levels in the upper range of normal are also at increased risk.

If your doctor has already prescribed thyroid hormone for you, and you have atrial fibrillation, get your thyroid hormone levels retested.  I can’t tell you how many atrial fibrillation cases I have seen from patients being prescribed too much thyroid hormone.

When it comes to atrial fibrillation risk from thyroid disease, it is generally because thyroid hormone levels are too high.  While studies have confirmed that an underactive thyroid is not generally a risk factor for atrial fibrillation, there are some reports that this may not always be the case.

4. Comprehensive Metabolic Panel (CMP)

A common blood test your doctor has probably already ordered for you is a comprehensive metabolic panel (CMP).  While what is contained within the CMP may vary from hospital to hospital, in general, it tests for electrolytes, kidney function, liver function, etc.

Depletion of certain electrolytes, like potassium and magnesium, is a clearly established atrial fibrillation risk factor.  Indeed, electrolyte optimization is critical to maintaining normal rhythm.  Fortunately, correcting electrolyte depletion is easy to do.  Simply, getting off diuretic medications, through weight loss, dietary optimization, and vigorous exercise works for many of my patients.  For those not on diuretics, boosting your intake of vegetables, fruit, legumes, nuts, and seeds usually corrects any electrolyte deficiency.  In rare cases, potassium or magnesium supplementation may be required.  Please don’t be tempted to correct electrolyte deficiencies with sports drinks as the sugar or artificial sweeteners are not worth the risk.

Poor kidney and liver function are also associated with atrial fibrillation.  Of course, with poor kidney or liver function, it is hard to know whether the kidneys or the liver caused the atrial fibrillation or the other way around. Regardless, if the goal is to beat atrial fibrillation, then both kidney and liver function needs to be optimized.  This may require consultation with a nephrologist (kidney specialist) or hepatologist (liver specialist).

5. Lipid Panel

Another test that has probably already been done for you is the lipid or cholesterol panel.  While your doctor likely ordered this blood test in the hopes of preventing atherosclerosis, abnormalities on this test may also predict your atrial fibrillation risk.

For example, studies show that high triglycerides predict atrial fibrillation. High triglycerides usually indicates that you are consuming too much sugar or flour (processed carbohydrates).  While your doctor will tell you that you want your triglycerides below 150 mg/dL, in my experience the lower your triglycerides the lower your atrial fibrillation risk.  Unless you have a genetic abnormality, a normal waist size, religious daily exercise, no sugar, no flour, and no eating after 7 PM should quickly get your triglycerides below 150.

In addition to triglycerides, a low HDL (good cholesterol) has also been associated with atrial fibrillation.  And if your HDL is low, follow The Atrial Fibrillation Diet, exercise daily, and get your waist size down to the normal range.

Your LDL, or “bad cholesterol,” is another important number for atrial fibrillation patients.  As strokes are the most feared atrial fibrillation risk, a recent study showed that an elevated LDL doubles your stroke risk.  And to keep your LDL as low as possible, strictly adhere to The Atrial Fibrillation Diet, never let a day go by without vigorous physical activity, and keep your body weight in the normal range.

6. Vitamin D

A low vitamin D level is associated with many chronic medical conditions–atrial fibrillation being no exception.  Indeed, a study of more than 27,000 people concluded that “low D” increases your atrial fibrillation risk by about 10%.

Now how exactly “low D” translates into an increased atrial fibrillation risk isn’t completely known.  However, studies suggest that it probably has something to do with increased inflammation through vitamin D receptors on cardiac cells, altered calcium metabolism, and fluid balance.

Of all the biomarkers to optimize, vitamin D has to be the easiest to correct.  Due to low vitamin D levels, I personally take 2000 IU daily when I don’t get a chance to get it naturally from the sun.  If your vitamin D levels indicate you also need to supplement, work with your physician to make sure you don’t take too much,  Indeed, our research suggests that too much vitamin D from supplements may also increase atrial fibrillation risk.

7. Anemia

From as far back as 1970, anemia has been recognized as an atrial fibrillation risk factor.  Anemia, or not enough red blood cells, not only is associated with atrial fibrillation but also indicates a potentially more dangerous case.   As with many of the other atrial fibrillation biomarkers in this article, your doctor has probably already tested for anemia.

When it comes to the causes of anemia, it generally comes down to one of two things.  Either you are losing blood somewhere in your body or your bone marrow can’t make enough red blood cells.  Anemia stresses your heart as your heart may not be able to get enough oxygen.  And any stress on the heart, physical or mental, increases the likelihood of atrial fibrillation.

Not only does anemia increase your atrial fibrillation risk but it also identifies an increased risk of something else bad happening like a heart attack, premature death, or stroke. If you have been diagnosed with both atrial fibrillation and anemia, be sure to work closely with your doctor to both correct the underlying cause of anemia and to minimize the risk of anything else bad happening.

8. Homocysteine

While a homocysteine blood test is easy for your doctor to order, it is rarely done.  Homocysteine is an amino acid and too much of this amino acid in your blood is associated with atrial fibrillation, strokesheart attacks, and dementia.

As with many of the other biomarkers covered in this article, the exact mechanism whereby too much homocysteine may trigger atrial fibrillation isn’t entirely clear.  Research has shown that high homocysteine levels may damage collagen in the heart thereby leading to cardiac scarring and enlargement of the left atrium.

So what should you do if your homocysteine levels are too high?  Like with vitamin D, optimizing this biomarker is surprisingly easy.  Just boost your vitamin B12 intake from fish, folate from green leafy vegetables and beans, and vitamin B6 from sweet potatoes, sunflower seeds, spinach, and bananas.  For those hoping to decrease homocysteine from taking supplements instead of eating real food, please note that many studies have shown that homocysteine-lowering vitamins don’t prevent bad things from happening to your heart.

9. BNP (B-type natriuretic peptide and N-terminal-pro-BNP)

There are two different ways your doctor can easily test for elevated levels of BNP.  And if you carefully review the medical literature there isn’t much difference between the B-type natriuretic peptide or the N-terminal-pro-BNP blood test.  As long as your doctor is testing for “BNP” it doesn’t really matter which test is chosen.

The bottom line is that BNP measures the physical stress your heart is experiencing.  BNP measures the degree of “heart failure” you have.  If your heart is pumping against high pressures, your body is retaining fluid, or heart inflammation is out of control your BNP will probably be high.  A “high BNP” is anything above 100 pg/mL for BNP  and anything above 125 pg/mL for NT-pro-BNP in people under age 75.

An elevated BNP is definitely something you don’t want.  A high BNP predicts an especially bad prognosis for atrial fibrillation as it is associated with heart failure, strokes, premature death, and recurrent atrial fibrillation.  If your BNP is up, you definitely need to see a cardiologist as soon as possible.  Medications will likely be needed until you can lower BNP naturally through weight loss, religious daily exercise, 100% clean eating, etc.

10. High Sensitivity Troponin (hs-Tn)

Having any troponin elevation in your bloodstream is a bad sign. Troponin is a heart muscle protein that signifies active heart muscle damage.

Indeed, an elevated troponin in someone with atrial fibrillation predicts a much higher risk of heart attack, heart failure, stroke, or premature death.  An elevated troponin also predicts that efforts to treat atrial fibrillation may not be as successful.

As with an elevated BNP, anyone with atrial fibrillation and an elevated troponin must be under the very close care of a cardiologist.  Fortunately, with prompt and aggressive therapy, including lifestyle optimization, BNP and troponin generally go down over time.

More Advanced Testing

In this article, we have covered the 10 most important atrial fibrillation blood tests that your doctor can easily order for you.  As you might imagine, these 10 tests are just the tip of the iceberg.

For example, you could be tested for chronic infections, food sensitivities, micronutrient deficiencies, hormonal imbalances, heavy metals, autoimmune diseases, vitamin deficiencies, etc. which all have been associated with atrial fibrillation in published studies.  However, to test beyond the 10 tests discussed above may require a functional medicine physician, naturopathic doctor, or other non-traditional health care providers with access to outside lab studies.


Lab testing is expensive and it isn’t always covered by insurance companies.  So it is best to check with your insurance company first before embarking on this path or you might get stuck with a big lab bill.



Disclaimer Policy: This website is intended to give general information and does not provide medical advice. This website does not create a doctor-patient relationship between you and Dr. John Day. If you have a medical problem, immediately contact your healthcare provider. Information on this website is not intended to diagnose or treat any condition. Dr. John Day is not responsible for any losses, damages or claims that may result from your medical decisions.

  1. This has been well presented and easily understood. Thank you for providing this info which I can share with my doctor before proceeding with drug therapy.

  2. Hello Dr Day
    Want to thank you for excellent blog topics on many interesting subjects full of good information. I thought you might find it interesting that in discovering a mold allergy that I was able to effectively deal with, I dropped two inflammatory markers dramatically. Those markers were Myeloperoxidase from 385 to 219 and NT-proBNP from 102 to 53 over a 3 month period. Elimination of the mold exposure was the only change in the 3 month period.
    Also, I would appreciate hearing your views on the positives vs. the negatives of the saturated fat of coconut oil and MCT oil. Thank you!