How Much Aspirin to Take to Lower Hematocrit - Dosage Guide

The Connection Between Aspirin and Hematocrit Levels

Hematocrit refers to the percentage of red blood cells in the blood. It is an important indicator of overall health. Normal hematocrit levels generally range from 34% to 50% for adult men and 30% to 45% for adult women. Higher than normal hematocrit levels, known as polycythemia, can thicken the blood and increase the risk of blood clots. On the other hand, lower than normal hematocrit levels, known as anemia, can reduce the blood's ability to carry oxygen throughout the body.

Aspirin is a common over-the-counter medication used to reduce fever, relieve pain, and lower the risk of blood clots. It works by inhibiting the production of prostaglandins, hormone-like substances that trigger inflammation and pain. Some research suggests that taking regular low-dose aspirin may also have an effect on hematocrit levels.

Aspirin's Impact on Hematocrit

A few small studies have found that taking regular low-dose aspirin (81 mg per day) may lower hematocrit levels, on average by 1% to 2%. This effect appears most pronounced in adults over the age of 70. Scientists think aspirin may lower hematocrit by inhibiting erythropoiesis, the process of red blood cell production in the bone marrow.

However, the effect is relatively small and hematocrit levels tend to stabilize with continued aspirin use. Larger drops in hematocrit are more likely to occur when first starting aspirin therapy. The effects also seem more pronounced in those who have a hematocrit level on the higher end of normal to start.

When the Drop in Hematocrit Becomes Concerning

For most people taking low-dose aspirin, the minor drop in hematocrit is not medically concerning. However, some individuals can experience larger than average decreases that may lead to anemia. This appears most likely to occur in adults over the age of 70.

In a 2021 study published in JAMA, researchers found taking 100 mg of aspirin per day led to anemia in nearly 1 out of every 8 adults over age 70 after just one year of use. Rates were even higher for adults in their 80s and 90s. The individuals most susceptible were those who had borderline anemia even before starting aspirin.

The findings suggest older adults looking to go on aspirin for primary prevention of cardiovascular disease should get baseline blood work including a hematocrit level. Those with borderline anemia may want to consider alternative therapies given their increased susceptibility.

Adjusting Aspirin Dosage to Balance Benefits and Risks

For older adults already taking low-dose aspirin who experience a concerning drop in hematocrit, there are a few options to balance the benefits and risks:

• Reduce aspirin dose: Taking 81 mg or less every other day may provide enough cardiovascular protection while limiting effects on hematocrit.
• Take iron supplements: Increasing iron intake can help support red blood cell production.
• Add vitamin B12/folic acid: Supplementing with these essential nutrients can also boost red blood cell counts.
• Stop aspirin if benefits no longer outweigh risks: If hematocrit drops significantly it may be time to re-evaluate if aspirin therapy is still appropriate.

Of course, any changes to medications or supplements should be discussed with a healthcare provider. They can monitor hematocrit levels and help determine the best course of action on an individual basis.

Other Factors That Can Lower Hematocrit

While regular aspirin use is one potential cause of reduced hematocrit levels in older adults, there are other medical reasons that should be considered as well:

• Gastrointestinal bleeding - Stomach ulcers, hemorrhoids, and other GI issues that cause internal bleeding over time can lead to anemia.
• Kidney failure - Damaged kidneys have a reduced ability to produce erythropoietin, the hormone that stimulates red blood cell production.
• Nutritional deficiencies - Lack of iron, vitamin B12, folate, and other nutrients needed to form red blood cells.
• Bone marrow disorders - Conditions affecting the bone marrow and its ability to produce blood cells.
• Cancers - Certain cancers and cancer treatments can suppress hematopoiesis.
• Genetic conditions - Some inherited disorders, like sickle cell disease, directly impact the production and lifespan of red blood cells.

Therefore, it's important for those experiencing anemia and low hematocrit to receive a full medical workup to determine the underlying cause. Addressing any primary conditions can help restore normal hematocrit levels, even while continuing aspirin if advised for cardiovascular health.

How Much Aspirin Lowers Hematocrit?

Most studies show that regular low-dose aspirin (81 mg per day) leads to a minor drop in hematocrit levels for adults over 70 years old. On average, hematocrit decreases by about 1 to 2 percentage points.

For example, someone with a starting hematocrit level of 42% may see that number drop into the 40% to 41% range after initiating daily aspirin. For otherwise healthy adults, this small change is unlikely to cause problems.

However, there can be larger than expected decreases in hematocrit among certain higher risk populations. Studies show adults over age 70 with borderline anemia may experience hematocrit reductions of over 3% on 100 mg per day of aspirin after just one year of use. Very elderly adults are also more prone to bleeding complications from aspirin that can dramatically lower hematocrit.

The effects of aspirin on hematocrit also appear somewhat dose dependent. While 81 mg aspirin tablets are commonly used in the U.S., lower doses from 20 mg to 40 mg are typical in Europe. The lower doses seem to carry a reduced risk of bleeding and hematocrit decline.

On the other hand, taking more than the recommended 81 mg per day does not provide any additional cardiovascular benefit but further raises the chance of bleeding issues. Therefore, sticking with the minimum effective aspirin dose is advised whenever possible.

Individual Factors That May Increase Hematocrit Drop

While aspirin consistently leads to minor reductions in hematocrit levels across populations, certain individuals may experience larger decreases. Risk factors include:

• Older age (over 70)
• Preexisting anemia or borderline low hematocrit
• Concurrent anticoagulant or NSAID medications that increase bleeding risk
• History of gastrointestinal ulcers or bleeding
• Poorly controlled high blood pressure
• Chronic kidney disease or reduced kidney function
• Vitamin deficiencies impairing red blood cell production
• Genetic conditions affecting hematopoiesis

For those at higher risk, more frequent monitoring of hematocrit levels is prudent upon starting aspirin therapy. This can help quickly identify any concerning drops in hematocrit so that treatment interventions or aspirin adjustments can be made.

Can Aspirin Be Used to Intentionally Lower Hematocrit?

In some cases, medications like aspirin are used to purposely reduce hematocrit levels. This is most often done when elevated hematocrit requires rapid lowering to avoid complications.

Some reasons aspirin may be used to intentionally decrease high hematocrit include:

• Polycythemia vera - A rare blood cancer leading to overproduction of red blood cells and excessive hematocrit levels.
• Low oxygen levels - Extended exposure to high altitude or lung conditions can trigger a spike in hematocrit.
• Chronic dehydration - becoming severely dehydrated can result in concentrated blood and increased hematocrit.
• Erythropoietin medications - These synthetic forms of erythropoietin used to treat anemia can sometimes elevate hematocrit to dangerous levels.

In these situations, doctors may prescribe aspirin to help bring down hematocrit to a safer range. The dose often needs to be higher than the 81 mg per day typically recommended for cardiovascular benefits. Doses may range from 325 mg once a day up to 650 mg four times per day as needed to reduce hematocrit.

Of course, taking aspirin just to lower hematocrit without clear medical cause is never advisable given bleeding risks. Those with elevated hematocrit should see a doctor to determine the underlying reason before taking any medication to correct it.

Monitoring Required When Using Aspirin to Reduce Hematocrit

When aspirin is used to intentionally lower hematocrit, close supervision by a healthcare provider is necessary. Hematocrit levels need to be checked frequently to make sure they are lowering to target levels but not dropping too far. Kidney function also requires monitoring since excess bleeding can impair the kidneys.

Once hematocrit reaches the ideal range, the aspirin dose often needs tapering to find the minimum amount necessary to maintain stable levels. People with conditions causing high hematocrit may need to remain on lifelong low-dose aspirin therapy.

If the cause of the high hematocrit is transient, like severe dehydration or a stint at high altitudes, then aspirin can be discontinued once levels normalize and the underlying trigger resolves.

In addition to hematocrit monitoring, those taking higher doses of aspirin for extended periods need to be checked regularly for potential complications like gastrointestinal bleeding and ulcers. Iron levels can also drop over time leading to iron deficiency anemia, which will then require supplementation.

Safe vs Unsafe Hematocrit Reductions

Mild reductions in hematocrit count are normal any time a medication like aspirin thins the blood. But how much of a decrease is safe vs unsafe? Here are some general guidelines:

• Safe: Drops of 1 to 3 percentage points, as long as hematocrit remains within or slightly below the normal range. Requires periodic monitoring.
• Borderline: Declines of more than 3 percentage points. Should prompt reassessment of the need for aspirin therapy vs alternative options.
• Unsafe: Hematocrit falling to significantly below normal levels for age and gender. Indicates medication adjustment or discontinuation may be required.

What qualifies as too low will depend on the starting hematocrit, health status, and individual risk factors. But generally hematocrit dropping into the mid to high 20s requires prompt medical attention to avoid complications of anemia.

Symptoms like fatigue, weakness, dizziness and shortness of breath can manifest once hematocrit falls outside the normal range. However, there may not be obvious symptoms until levels become severely low. Relying on regular hematocrit testing is important.

For at risk individuals like the elderly and those with preexisting anemia or bleeding disorders, smaller drops in hematocrit may be concerning even if still in the low normal range. Their health providers can advise specific thresholds for medication change or discontinuation as needed.

When to Seek Medical Evaluation

In addition to monitoring hematocrit levels through routine blood work, be sure to contact a doctor if any of the following signs of excessive bleeding develop while taking aspirin:

• - Black, tarry stools
• - Bright red blood in vomit
• - Coffee ground appearing vomit
• - Severe stomach pain
• - Coughing up blood
• - Blood in the urine
• - Heavy vaginal bleeding
• - Frequent nosebleeds
• - Bleeding gums
• - Unusual bruising
• - Lightheadedness
• - Changes in stool color

Prompt medical help for suspected internal bleeding can lower the chance of needing hospitalization or transfusions to reverse the resulting anemia. Do not stop aspirin use on your own without guidance, as this could further increase clotting risks.

Tips for Maintaining Healthy Hematocrit Levels

While some medications like aspirin can impact hematocrit levels, certain lifestyle measures may help counteract reductions to an extent:

• Stay well hydrated - Drink plenty of non-alcoholic fluids to maintain blood volume.
• Increase iron intake - Eat iron-rich foods or consider supplements if levels low.
• Eat more fiber - Prevent constipation and GI bleeding.
• Don't smoke - Smoking impairs red blood cell production.
• Limit alcohol - Excess alcohol can lead to low B12, folate, and iron levels.
• Manage other conditions - Effectively control high blood pressure, diabetes, kidney disease and other hematocrit-impacting illnesses.
• Exercise regularly - Physical activity supports healthy hematopoiesis.

Additionally, avoiding use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen whenever possible can help reduce combined effects on hematocrit when taking low-dose aspirin. Acetaminophen is typically considered safer for those who also need aspirin therapy.

Of course, speak to your healthcare provider before making any major changes to diet, supplements, or medications. They can provide personalized guidance on maintaining healthy hematocrit levels based on your medical history and baseline lab results.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.