What are normal CRP levels?

Normal CRP levels | CRP test | High CRP levels | Causes | Symptoms | How to lower CRP levels

A CRP test measures blood levels of a substance called C-reactive protein (CRP). But what is C-reactive protein? The liver produces CRP in response to inflammation in the body. Inflammation is the body’s healing response. When a wound or injury swells, reddens, and hurts, that’s one form of inflammation, and it’s the body’s natural reaction to trauma, infection, and disease.

The inflammatory process prompts the immune system to send healing white blood cells to the affected area. These first responder cells produce chemicals, called cytokines, that make the blood vessels larger, allowing more blood, oxygen, and cells to the area. The increased blood flow causes redness, warmth, and swelling. In acute inflammation, the body responds appropriately to harm or infection, and the process lasts from hours to several days. However, in chronic inflammation, the response persists, and the body remains in a state of high alert. This low-grade inflammation may begin damaging healthy tissues and causing problems throughout the body. As a result, chronic inflammation is thought to be harmful and can contribute to cardiovascular disease, cancer, and other chronic health conditions.

When inflammation occurs, the concentration of serum proteins called acute phase reactants increases. CRP is one of the acute phase reactants. C-reactive protein tests are a type of inflammation blood test that help healthcare providers identify inflammation and monitor the effectiveness of ongoing treatment. Inflammation is a complex, highly orchestrated process that involves many different cell types. These different cells can initiate, amplify, sustain, or get rid of inflammation. They are also a predictor of cardiovascular disease. This article describes what CRP tests are and helps explain the meaning of different CRP levels.

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What are normal CRP levels?

Laboratories measure CRP in milligrams of CRP per liter of blood (mg/L). In healthy adults, normal CRP levels should be less than 3 mg/L, although reference ranges vary. In fact, the level of CRP that is truly normal is not known. Typically, CRP levels above 3.0 mg/L indicate inflammation. CRP value also normally increases with age, in African American individuals, and in females. 

The table below shows what the different CRP levels could indicate. But bear in mind that these ranges vary slightly between laboratories.

How is CRP tested?

The C-reactive protein test requires a blood test, usually from a vein in the arm. It shouldn’t hurt aside from a slight sting when the needle enters and leaves the vein to take a blood sample. There’s usually no special preparation like fasting or avoiding liquids before the test. 

Factors that can affect CRP levels

Certain factors affect C-reactive protein levels, including:

• Medications: Some cholesterol-reducing medicines (statins) and nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce inflammation and lower CRP levels.
• Exercise: Strenuous exercise can spike CRP levels, so it’s best to avoid a hard workout right before your blood draw. 

• Recent injuries or infection: Even minor conditions can cause a temporary increase in C-reactive protein levels. This may then conceal other chronic conditions such as diabetes or cardiovascular disease.
• Magnesium supplementation: This may decrease C-reactive protein levels in some people. Ask your provider about whether you should stop taking supplements before having your blood drawn.
• Hormone levels: Individuals using estrogen-based birth control or hormone replacements may have increased CRP levels. Likewise, pregnancy may elevate C-reactive protein levels, particularly during the later stages.
• Other factors: Certain individuals may have higher baseline CRP levels including women, seniors, smokers, and people with diabetes, obesity, or depression.

When a doctor may order a CRP test

Your physician may order a C-reactive protein test if you have symptoms of a serious bacterial or viral infection, such as:

• Fever or chills
• Nausea and vomiting
• Irregular heart rate
• Rapid breathing

Your healthcare provider may also request a CRP blood test to monitor ongoing treatment if you have a chronic autoimmune disease like lupus or rheumatoid arthritis to monitor for level of current inflammation. If treatment is working, inflammation and C-reactive protein levels should drop. 

Typically, CRP lab tests are fast and accurate. However, if your test results show that you have only slightly elevated C-reactive protein levels, the test can be challenging to interpret because of numerous potential conditions that can cause this effect. High CRP is a biomarker, meaning it’s one factor to consider when assessing someone’s health, but it does not give a source of inflammation. A high CRP level is not a stand-alone diagnosis.

Because primary healthcare providers cannot always draw solid conclusions from levels of C-reactive protein alone, they may also order other tests to provide a more comprehensive overview of your health.

C-reactive protein can also act as a predictor of coronary heart disease. If you have risk factors of heart disease, your provider may order a high-sensitivity C-reactive protein test. The hs-CRP test, or high-sensitivity CRP test, is a special CRP test that detects lower levels of CRP in the blood than the routine CRP lab test detects. The hs-CRP level is from 0.5–10 mg/L. Levels above 3 mg/L are considered high risk for developing cardiovascular disease.

What is considered a high CRP level?

Anything above 10 mg/L, or a minor elevation, may be considered a high CRP level. Generally, “a CRP reading greater than 10 mg/L is considered dangerous,” says Daniel Boyer, MD, researcher at the Farr Institute in West Des Moines, Iowa. “It is likely caused by a severe bacterial infection and indicates acute inflammation that requires further tests to determine the cause of the inflammation.”

What causes high CRP levels?

High CRP levels tend to occur with severe bacterial or fungal infections, such as sepsis, osteomyelitis, pneumonia, urinary tract infection, or endocarditis. In fact, infections are responsible for 90% of cases involving CRP levels of 50 mg/L or greater. An extensive range of risk factors can cause mild or moderately raised CRP levels, including:

• Viral illness, like COVID-19
• Pregnancy
• Depression
• Diabetes
• Obesity
• Smoking
• Heart attack (myocardial infarction)
• Cancer
• Bronchitis
• Sedentary lifestyle
• Inflammatory conditions or autoimmune diseases like inflammatory bowel disease, lupus, or rheumatoid arthritis

CRP levels and COVID-19

CRP levels increase in people infected with SARS-CoV-2, the virus that causes COVID-19. Severe COVID-19 infections causes an overproduction of inflammatory cytokines and interleukins. Although these chemical messengers help the body fight the virus, they can damage lung tissue when the immune system overreacts. Together, the inflammatory cytokines and tissue destruction increase CRP production.

CRP is not a diagnostic test. CRP levels indicate inflammation in the body. Elevated CRP does not mean someone has a COVID-19 infection. That said, in many cases, patients with COVID-19 have a significant increase in CRP levels with concentrations on average 20 to 50 mg/L. The highest CRP concentrations indicate someone has a more severe infection and probable lung damage.

RELATED: What we know about sequelae and lingering COVID-19 symptoms

Symptoms of high CRP

The symptoms of high CRP levels depend on the underlying condition causing the inflammation. It’s possible to have high CRP levels with no symptoms. If you have a moderate infection or injury that causes inflammation, symptoms may include:

• Aches and pains 
• Fatigue
• Unexplained weight loss
• Bloating
• General malaise
• Low-grade fever
• Chills
• Gastrointestinal problems, such as nausea, loss of appetite, or indigestion
• Headaches
• Difficulty sleeping or insomnia
• Tiredness

How to lower CRP levels

There’s a range of dietary and lifestyle changes that can help lower CRP levels. Additionally, a primary healthcare provider may prescribe medication if appropriate.

1. Treat the underlying condition

“The most important step you should take is to work with your doctor to determine why it is elevated,” says Leann Poston, MD, medical advisor for Impakt Fitness. Treating the condition causing inflammation is essential to reducing an elevated CRP level. Depending on the underlying cause, the following may lower CRP levels. 

2. Weight loss  

Losing even a small amount of weight can help reduce CRP levels. In one study, participants who lost just 5% of their total body weight and fat mass more than doubled the odds of achieving desirable CRP levels.

3. Exercise

Elevating the heart rate and engaging in regular physical activity may reduce CRP levels caused by a sedentary lifestyle. And the good news is that the amount of exercise someone needs to lower CRP levels isn’t much. Researchers estimate that total energy expenditure of around 1,000 calories per week can help.

4. Mindset

Mental outlook can affect your body and CRP levels. For example, in an extensive study of nearly 7,000 people, those with a more pessimistic mindset had increased CRP levels. Mindfulness practices, meditation, and yoga can help your alter your mental outlook.

Cannabis

A primary healthcare provider may recommend medical cannabis. In a survey of 9,000 adults, those who recently used cannabis had lower CRP levels than others. Another study of over 10,000 people found that elevated CRP levels were significantly higher among non-marijuana users. Discuss the potential risks and benefits with your physician.  

5. Diet

To help lower systemic inflammation and CRP levels, “eat a multi-colored diet, one that is high in fiber and rich in fruits and vegetables. A Mediterranean-style diet is an excellent choice,” Dr. Poston says. Good foods to include are:

• Apples
• Avocados
• Bananas
• Beans and legumes
• Cruciferous vegetables like Brussels sprouts and broccoli
• Pears
• Strawberries
• Whole grains

Consuming a small amount of alcohol, such as a glass of wine, can help lower CRP levels more than avoiding alcohol altogether. The type of alcohol appears irrelevant, as long it’s in moderation (not more than seven alcoholic drinks a week for women or 14 for men).

Other worthwhile beverages to consider include coffee and green tea. It seems that higher coffee consumption and lower CRP go hand in hand. Likewise, compounds in green tea may reduce markers of inflammation, including CRP.

RELATED: What’s the best diet for inflammation?

6. Supplements

“Supplements may also lower CRP levels,” says Dr. Boyer. Omega-3 fatty acids can reduce inflammation according to the American Heart Association. Additionally, some research shows that vitamin D can reduce inflammation, and CRP levels.

RELATED: When would I need a prescription for vitamin D?

7. Medication

To help address the underlying cause for your high CRP, your physician may recommend medication. If the CRP elevation is due to an autoimmune issue or infection, immune modulating medications or antibiotics may be used. If your baseline CRP is high, with no other medical conditions, “Pharmacological treatment involves taking angiotensin receptor blockers (ARBs) or other cholesterol-lowering medications,” says Dr. Boyer. Statins are another type of cholesterol-lowering medication. Research shows that they can reduce CRP levels by up to 50%.