How Do I Know If My Fatigue Is Long COVID or ME/CFS?

Up to 50% of people with Long COVID also meet the diagnostic criteria for ME/CFS by six months.

If you’ve been living with crushing fatigue for months, you might be asking yourself a frustrating but important question: Is this Long COVID, or could it be ME/CFS? Both conditions can feel nearly identical. They’re exhausting. They’re disruptive. And when your lab tests come back “normal,” it can feel like no one takes it seriously. But there are real patterns, and even though there’s no perfect test, you can start to make sense of what your body is telling you.

This guide walks you through the key differences, similarities, and next steps to get clarity and support.

Why Long COVID and ME/CFS Are Hard to Tell Apart

Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) share so many symptoms that even clinicians often struggle to tell them apart. Both involve:

• Persistent, disabling fatigue

• Post-exertional malaise (PEM)

• Brain fog and memory issues

• Sleep disturbances

• Muscle pain or weakness

• Dizziness or lightheadedness

• Digestive complaints

These symptoms often don’t improve with rest and can fluctuate unpredictably. On a clinical level, the overlap is substantial. Objective measures like exercise testing or cognitive screening typically don’t distinguish the two conditions. That makes diagnosis rely heavily on history and pattern recognition.

The One Clear Difference: Timing and Trigger

The most consistent way to differentiate between Long COVID and ME/CFS is the timeline of onset.

Long COVID fatigue begins within a few weeks or months of a confirmed or likely COVID-19 infection. The fatigue may start right after the illness or emerge a bit later, but the connection is usually clear.

ME/CFS, on the other hand, may be triggered by a wide range of events, including viral infections (like Epstein-Barr), bacterial infections, surgery, or even emotional trauma. In some cases, no clear trigger is ever identified.

To meet diagnostic criteria for ME/CFS, your symptoms must last for at least six months, significantly impair daily functioning, and not be better explained by another diagnosis. Long COVID can be identified earlier, especially if the connection to COVID-19 is well documented.

Subtle Differences in Symptoms

Some researchers have identified minor trends that may help in distinguishing the two conditions, though these are not definitive:

ME/CFS may include:

• More frequent reports of unrefreshing sleep

• More noticeable memory and word-finding problems

• Muscle weakness and joint pain

• Enlarged or tender lymph nodes

Long COVID may include:

• More respiratory symptoms, such as shortness of breath or chest pressure

• Clear timeline connecting symptom onset to COVID-19

• Greater likelihood of symptoms involving the heart or autonomic nervous system (e.g., POTS)

Again, there is wide variability. Many Long COVID patients meet all criteria for ME/CFS by month six. Some ME/CFS patients develop new symptoms over time that resemble Long COVID patterns. This blurring of lines is why clinicians must rely on history rather than one test or symptom list.

Can Lab Tests or Imaging Help?

Unfortunately, neither condition has a reliable biomarker. Routine labs often appear normal, and imaging typically doesn’t reveal abnormalities unless another condition is also present.

However, testing still matters. It can help rule out other causes of fatigue, such as:

• Anemia

• Thyroid disease

• Autoimmune conditions

• Adrenal insufficiency

• Heart or lung problems

Some research shows that Long COVID may be associated with subtle endocrine, vascular, or immune changes, including low cortisol, disrupted blood flow, or autoantibodies. But these findings are not unique to Long COVID and are not specific enough for diagnosis.

What to Do If You're Still Unsure

1. Track your symptoms over time. Write down when they started, how they change, and what triggers crashes.

2. Get basic labs to rule out common issues like thyroid problems or anemia.

3. See a clinician who has experience with both conditions.

4. Understand that you might meet both criteria, especially if your fatigue persists beyond six months post-COVID.

5. Focus on management, not just diagnosis. Many care strategies overlap.

Strategies That Help in Both Conditions

Regardless of the label, certain support strategies benefit both Long COVID and ME/CFS:

• Pacing: Avoid overexertion to prevent crashes.

• Nervous system regulation: Breathing exercises, grounding, and reducing overstimulation.

• Blood sugar balance: Regular meals to support energy and brain function.

• Sleep hygiene: Light cues, screen limits, and a consistent rhythm.

• Gentle movement (if tolerated): Stretching or reclined activity with close attention to symptoms.

If you’re stuck in a cycle of exhaustion and your health feels unpredictable, you’re not alone—and it’s not all in your head. Whether your fatigue is rooted in Long COVID or ME/CFS, it’s valid, real, and worthy of care. Diagnosis is helpful, but it’s not everything. What matters most is finding a path that supports your body where it is today.

Need help organizing your history or figuring out your next steps? Try our free nervous system reset tool below.

Further Reading:

1. Half of Long COVID Patients Meet ME/CFS Criteria

2. Long COVID – Wikipedia Overview

3. Post-Exertional Malaise in Long COVID and ME/CFS

4. Skeletal Muscle Abnormalities in Long COVID

5. Immune and Symptom Profiles in ME/CFS and Long COVID

6. Physical Capacity and Fatigue in Long COVID and ME/CFS

7. CDC: Long COVID Signs and Symptoms

8. Post-Exertional Malaise as a Hallmark of ME/CFS

9. ME/CFS and Long COVID: Similarities and Differences