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Severe Illness Blood Test

What is Severe Illness?

Severe illness encompasses critical medical conditions that significantly impact the body's normal functioning and multiple organ systems. During critical illness, the body undergoes metabolic stress that commonly triggers non-thyroidal illness syndrome, where free thyroxine (T4) levels become altered. The Thyroxine Free, Direct Dialysis (FT4) test is the most important test for monitoring metabolic function and distinguishing illness-related thyroid changes from true thyroid disease during severe illness.

RECOMMENDED TEST Thyroxine Free, Direct Dialysis (FT4)
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Fast & easy, results by email & SMS
No extra fees paid at the lab
No need to visit a doctor
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No insurance needed
Results explained
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What causes severe illness complications?

Severe illness complications are caused by the body's systemic stress response to critical medical conditions that affect multiple organ systems simultaneously. During severe illness, physiological stress triggers metabolic disruptions, immune system dysregulation, and hormonal imbalances that can lead to secondary complications. One of the most common complications is non-thyroidal illness syndrome, where the body's metabolic adaptation causes alterations in thyroid hormone levels even when the thyroid gland itself is functioning normally, which can significantly impact recovery and prognosis.

What is the best test for severe illness monitoring?

The Thyroxine Free, Direct Dialysis (FT4) test is the most important test for monitoring severe illness because it detects metabolic changes that commonly occur during critical illness. This test measures free thyroxine (T4), the active thyroid hormone that regulates metabolism throughout the body. During severe illness, free T4 levels typically decrease due to non-thyroidal illness syndrome, and monitoring these levels helps healthcare providers assess how the illness is affecting metabolic function and distinguish between illness-related thyroid changes and actual thyroid disease. This information is essential for managing treatment and predicting recovery outcomes in critically ill patients.

When should I get tested for severe illness complications?

You should get tested if you are currently hospitalized or recovering from a critical medical condition, experiencing prolonged illness lasting several weeks or months, or if your healthcare provider suspects metabolic complications during your illness. Testing is particularly important if you have symptoms of metabolic dysfunction such as unexplained fatigue, temperature regulation problems, or changes in heart rate that persist during or after severe illness. Early detection of complications like non-thyroidal illness syndrome through FT4 testing can help guide treatment decisions and monitor your recovery progress.

What are the symptoms of severe illness?
Symptoms of severe illness vary depending on the underlying critical condition but commonly include extreme fatigue and weakness, difficulty breathing or shortness of breath, altered mental status or confusion, persistent high fever or inability to regulate body temperature, rapid heart rate or blood pressure changes, and significantly decreased ability to perform daily activities. During severe illness, you might also notice symptoms related to metabolic complications such as unexplained weight changes, muscle weakness, or persistent exhaustion that seems disproportionate to your activity level. These systemic symptoms reflect the body's struggle to maintain normal functioning under extreme physiological stress.
Who is at risk for severe illness complications?
People with chronic medical conditions such as diabetes, heart disease, kidney disease, or lung disease are at higher risk for developing complications during severe illness. Elderly individuals and those with weakened immune systems are particularly vulnerable to metabolic disruptions like non-thyroidal illness syndrome. Patients requiring intensive care, those with sepsis or multi-organ failure, individuals undergoing major surgery, and people experiencing prolonged hospitalization face increased risk of developing secondary complications. Additionally, patients with pre-existing thyroid disorders may be at greater risk for more severe metabolic changes during critical illness.
What happens if severe illness complications are left untreated?
Untreated complications during severe illness can lead to prolonged recovery times, worsening of the underlying critical condition, and potential progression to multi-organ failure. Non-thyroidal illness syndrome, when unrecognized, can complicate treatment decisions and make it difficult to distinguish between illness-related metabolic changes and actual thyroid disease requiring intervention. Failure to monitor and manage metabolic complications can result in poor nutritional status, increased risk of infections, cardiovascular complications, and significantly increased mortality risk. Early detection and monitoring through blood tests like FT4 can help prevent these serious outcomes and guide appropriate supportive care.
Can severe illness complications be diagnosed with a blood test?
Blood tests are essential for monitoring complications during severe illness, though the diagnosis of the underlying critical condition is typically based on clinical presentation and specific diagnostic criteria. The FT4 blood test specifically detects non-thyroidal illness syndrome by measuring free thyroxine levels, which become altered during severe illness. Blood tests also assess organ function, electrolyte balance, inflammatory markers, and nutritional status, providing crucial information about how the illness is affecting your body. While these tests cannot diagnose the initial severe illness itself, they are vital tools for detecting secondary complications, monitoring disease progression, and guiding treatment decisions throughout your critical illness.
How is severe illness treated?
Treatment of severe illness depends on the specific underlying critical condition and typically requires hospitalization with intensive supportive care. Management focuses on addressing the primary illness while supporting vital organ function through interventions such as oxygen therapy, fluid resuscitation, medications to stabilize blood pressure, and nutritional support. For metabolic complications like non-thyroidal illness syndrome, treatment is generally supportive rather than involving thyroid hormone replacement, as the condition typically resolves when the underlying illness improves. Close monitoring through regular blood tests helps healthcare providers adjust treatment plans, manage complications, and assess recovery progress throughout the critical illness period.
How can I prevent severe illness complications?
Preventing complications during severe illness requires early medical intervention at the first signs of critical illness, adherence to prescribed treatments for chronic conditions that increase vulnerability, and maintaining regular follow-up care with healthcare providers. Seeking immediate medical attention for serious symptoms such as difficulty breathing, chest pain, severe infections, or altered mental status can prevent progression to more severe complications. During illness, following medical advice carefully, maintaining adequate nutrition and hydration, getting sufficient rest, and attending all scheduled monitoring appointments including blood tests can help detect complications early. For individuals with chronic conditions, keeping these well-controlled through medication compliance and lifestyle management reduces the risk of developing severe illness.
What can I do at home to support recovery from severe illness?
Recovery from severe illness requires patience and careful attention to your body's needs, including getting plenty of rest and gradually increasing activity levels as tolerated. Focus on consuming nutrient-dense foods with adequate protein to support healing, staying well-hydrated, and taking all prescribed medications exactly as directed. Monitor your symptoms closely and report any concerning changes to your healthcare provider immediately, such as worsening fatigue, breathing difficulties, or new symptoms. Attend all follow-up appointments and recommended blood tests to ensure complications are detected early. While recovering, avoid smoking and excessive alcohol, manage stress through gentle activities like meditation or light stretching, and ask for help with daily tasks when needed rather than overexerting yourself during the healing process.
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Long story short:
  1. In the test options, use the filters or search box to narrow your choices and find the test you want.
  2. If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test.
  3. Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout.
  4. If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want.
  5. When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system.
  6. Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way.
  7. You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy!
  8. If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.
How do I know which test to get?
In the test options, find the test you want. If you’re not sure which test to get, we can lend a hand in finding the right option.

Just text or call us at 754-799-7833, email us at support@privatemdlabs.com, and we'll gladly help you. We've got your back and reply quickly.
Is it possible to make changes to my lab order if I made a mistake with the name, date of birth, or any other details?
Absolutely! We totally understand that errors can happen. No worries, we're here to help you.

Just reach out to us via text at 754-799-7833 or shoot us an email at support@privatemdlabs.com. Remember to include your order number and let us know the correct information you’d like to update. Our awesome team will jump right in and make sure everything is sorted out and accurate for you.

There are no changes necessary if your address is wrong on the requisition though. We don’t mail anything out.

Our lab requires an address to be listed to generate an order.
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Only HSA & FSA is accepted.

Our services are strictly self-pay and cannot be submitted to your health insurance provider except for Health Savings Accounts or Flexible Savings Accounts.

This policy applies to all insurance companies, including federal health insurance programs like Medicare.

If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com.
Can I cancel my order?
Yes.

We get it – sometimes your needs change.

As long as your samples haven’t been collected yet, we’re happy to help you cancel your order.

If you have any further questions, please text us at 754-799-7833 or email support@privatemdlabs.com.

You can read more about our cancellation policy here.
How can I find a lab location near me?
During the ordering process, you’ll be able to select a specific lab near you, with no strings attached! You can switch it up later easily and visit any of our authorized locations as long as it’s the same lab company you selected your test for (Quest Diagnostics or Labcorp).

Before you proceed with your order, feel free to browse through all our lab locations here. This will give you the peace of mind of knowing that there's a lab nearby your home, office or your favorite gym.

If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.
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* Regular blood test results (e.g., CBC) typically start arriving the next business day after sample collection. More complex tests, such as hormone panels, may take up to 10–15 business days due to their complexity.

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Thyroxine Free, Direct Dialysis (FT4)
What's included
Fast & easy, results by email & SMS
No need to visit a doctor
Private & confidential
No insurance needed
Results explained
No extra fees paid at the lab

Sample results

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