Long COVID and Sticky Microclots: The Hidden Blood Changes Behind Fatigue and Brain Fog

Months after a COVID-19 infection, many patients tell me they still don’t feel like themselves. They describe crushing fatigue, brain fog that won’t lift, shortness of breath, and a sense that their body is “off.” Standard lab tests often come back normal. That can be frustrating and even discouraging.

Now, emerging research is offering a possible biological explanation. Scientists have identified unusual, persistent microclots in the blood of people with long COVID. These are not the large clots that cause strokes or pulmonary embolisms. They are microscopic, but they may still interfere with oxygen delivery and drive inflammation in subtle yet meaningful ways.

Here’s what we know so far, and what symptoms you should be watching for.

What Are Microclots — And Why Do They Matter?

Your body forms blood clots for a good reason: to stop bleeding after an injury. Under normal circumstances, clots are temporary. They form, seal a wound, and then dissolve through a natural process called fibrinolysis.

Microclots are different.

Researchers studying long COVID have found that some patients develop tiny clots, often 1–200 micrometers in size, that persist in circulation. Unlike typical clots, these appear to contain misfolded fibrin proteins with amyloid-like characteristics. This structural change may make them more resistant to breakdown.

In one study, patients with long COVID had nearly 20 times more microclots than healthy controls. Even more striking, these clots were often embedded with neutrophil extracellular traps (NETs), sticky webs of DNA released by immune cells during infection. While NETs help trap pathogens, excessive or prolonged NET formation can promote inflammation and clot stability.

When microclots resist breakdown, they may obstruct capillaries — the smallest blood vessels responsible for delivering oxygen and nutrients to tissues. Even minor impairments at this level can contribute to systemic symptoms over time.

The NET Connection: Why These Clots Are So Sticky

Neutrophils are white blood cells that defend you against infection. During severe immune activation, they release NETs, which are strands of DNA and enzymes designed to trap viruses and bacteria.

In long COVID, elevated levels of NETs have been observed. Recent research suggests that these DNA webs physically associate with microclots, reinforcing their structure and making them harder to dissolve.

This creates a potential cycle:

1. Viral remnants or inflammatory signals trigger immune activation.
2. Neutrophils release NETs.
3. NETs bind to abnormal fibrin and stabilize microclots.
4. Persistent microclots contribute to reduced blood flow and ongoing inflammation.

The result may be a form of thromboinflammation — where clotting and immune activation feed into each other.

This mechanism is still under investigation, and more large-scale studies are needed. But the pattern is compelling enough that researchers are exploring whether microclots and NET markers could eventually serve as diagnostic tools for long COVID.

Key Symptoms Linked to Microclots in Long COVID

While research is ongoing, the proposed effects of microclots align with many of the most common long COVID symptoms.

1. Persistent Fatigue

If microclots impair oxygen delivery at the capillary level, your muscles and organs may not receive optimal oxygen. Even mild reductions in tissue oxygenation can leave you feeling exhausted after minimal exertion.

2. Brain Fog

Your brain is highly sensitive to changes in blood flow and inflammation. Subtle circulation issues, combined with inflammatory signals, may contribute to memory lapses, slowed thinking, and difficulty concentrating.

3. Shortness of Breath

Even if your lungs appear structurally normal, microvascular changes could affect oxygen exchange efficiency, leading to a feeling that you can’t take a satisfying breath.

4. Chest Tightness or Palpitations

Inflammatory and clotting abnormalities may influence cardiovascular function, causing discomfort or irregular heart sensations in some patients.

5. Exercise Intolerance

Many long COVID patients report post-exertional symptom flares. If blood flow is compromised at the microvascular level, increased demand during activity may overwhelm the system.

It’s important to remember that these symptoms can have multiple causes. Microclots are one possible piece of a complex puzzle.

How Microclots Differ From Typical Blood Clots

Traditional blood clots, such as those seen in deep vein thrombosis, are larger and often detectable with imaging. They can cause acute, life-threatening events.

Microclots are much smaller and may not show up on standard diagnostic tests. Their composition also appears different. Research suggests that the fibrin within these clots may adopt an amyloid-like configuration, meaning the protein folds abnormally and becomes more resistant to enzymatic breakdown.

Additionally, microclots may trap inflammatory molecules and inhibitors of fibrinolysis, such as alpha-2-antiplasmin, further reducing the body’s ability to clear them efficiently.

These structural differences could explain why symptoms persist long after the initial viral infection has resolved.

Can Microclots Be Treated?

There is currently no widely approved, standardized treatment specifically targeting microclots in long COVID.

Some small, preliminary studies have explored combinations of antiplatelet and anticoagulant therapies under careful medical supervision. While some patients reported symptom improvement, these approaches carry bleeding risks and require close monitoring. They are not appropriate for self-treatment.

Other strategies under investigation include therapies aimed at reducing inflammation, improving endothelial health, and supporting natural fibrinolysis.

For now, management focuses on symptom support, rehabilitation, and reducing overall inflammatory burden while research continues.

Why This Matters for You

Long COVID is not “just in your head.” The identification of microclots and NET involvement suggests measurable, biological changes may underlie persistent symptoms.

At the same time, this research is still evolving. We need larger trials to establish cause-and-effect relationships and to determine who is most at risk.

If you are experiencing ongoing symptoms after COVID-19, speak with your healthcare provider. Comprehensive evaluation is essential, as symptoms like fatigue and brain fog can also stem from thyroid dysfunction, anemia, sleep disorders, or mood conditions.

Knowledge empowers you to ask better questions and seek appropriate care.

My Personal RX on Supporting Healthy Blood Flow and Recovery

When facing a condition as complex as long COVID, you want to focus on what you can control. While we await more definitive treatments, there are science-based strategies that support vascular health, immune balance, and overall recovery.

Here are my recommendations:

1. Reduce Systemic Inflammation Through Diet: Focus on an anti-inflammatory eating pattern rich in leafy greens, berries, fatty fish, olive oil, nuts, and legumes. These foods support endothelial function and healthy circulation.
2. Support Gut-Immune Balance: Your gut microbiome influences systemic inflammation. A high-quality probiotic and adaptogenic blend like MindBiotic can help support digestive and immune health, which may indirectly benefit inflammatory regulation.
3. Stay Hydrated: Proper hydration helps maintain blood viscosity and circulation. Aim for consistent water intake throughout the day.
4. Move Gently but Consistently: Light activity such as walking or stretching can support circulation without overexertion. If you experience post-exertional symptom flares, pace yourself carefully.
5. Prioritize Sleep: Deep sleep is when your body repairs tissues and regulates immune activity. Aim for 7–9 hours nightly.
6. Manage Stress Signals: Chronic stress can worsen inflammatory pathways. Guided breathing exercises or mindfulness programs like Calm the Chaos can help regulate your stress response.
7. Consider Digestive Support: If you’re struggling with bloating or digestive discomfort after COVID, Digestive Enzymes may help optimize nutrient absorption, supporting recovery.
8. Monitor Nutrient Levels: Work with your physician to assess vitamin D, iron, B12, and other key markers that influence energy and immune function.
9. Educate Yourself on the Gut-Brain Link: Understanding how inflammation affects cognition can be empowering. In my book Heal Your Gut, Save Your Brain, I discuss how supporting gut health can benefit brain clarity and resilience.
10. Partner With a Knowledgeable Clinician: Long COVID care often requires a team approach. Seek providers who take your symptoms seriously and are up to date with emerging research.

Your recovery journey may not be linear, but progress is possible. Science is moving forward, and with thoughtful lifestyle strategies, you can support your body as it heals.

Source:

1. Thierry, A. R., Usher, T., Sanchez, C., Turner, S., Venter, C., Pastor, B., Waters, M., Thompson, A., Mirandola, A., Pisareva, E., Prevostel, C., Laubscher, G. J., Kell, D. B., & Pretorius, E. (2025). Circulating microclots are structurally associated with neutrophil extracellular traps and their amounts are elevated in long COVID patients. Journal of Medical Virology, 97(10), e70613. https://doi.org/10.1002/jmv.70613