“I’m Always Tired”: A St. Augustine, FL Primary Care Doctor’s Guide to the Medical Workup of Fatigue

“I’m Always Tired”: A St. Augustine, FL Primary Care Doctor’s Guide to the Medical Workup of Fatigue

As a primary care doctor, one of the more common concerns my patients bring up is fatigue. Sometimes it’s described as “low energy,” “feeling drained,” or “just not like myself lately.” While it may sound vague, fatigue is a very real and distressing symptom that can significantly impact daily life, productivity, and emotional well-being. The tricky part? Fatigue is nonspecific, meaning it can stem from many different causes — from lifestyle habits to serious medical conditions.

This blog post aims to shed light on how we approach fatigue in primary care, the most common medical causes, and what kind of diagnostic workup is typically involved.

Understanding Fatigue

Fatigue is more than just feeling sleepy. It refers to a persistent lack of physical or mental energy that doesn’t resolve with rest. When someone tells me they feel fatigued, I ask them to describe their symptoms more specifically:

• Is the fatigue physical (e.g., body feels heavy) or mental (e.g., brain fog)?

• Is it constant or does it come and go?

• How long has it been going on?

• Does it interfere with daily life?

• Are there other symptoms, like weight loss, trouble sleeping, mood changes, or shortness of breath?

These answers help guide the direction of the medical workup.

Common Medical Causes of Fatigue

While the causes of fatigue are numerous, here are some of the most common conditions we consider in primary care:

1. Anemia

Anemia — or a low red blood cell count — reduces the body’s ability to carry oxygen to tissues, leading to fatigue, shortness of breath, and sometimes dizziness or cold hands and feet. Iron-deficiency anemia is most common, but we also look for B12 or folate deficiency and chronic disease-related anemia.

2. Thyroid Disorders

An underactive thyroid (hypothyroidism) is a classic cause of fatigue. Other symptoms may include weight gain, constipation, dry skin, depression, and feeling cold all the time. Overactive thyroid (hyperthyroidism) can also cause fatigue, although it’s typically accompanied by weight loss, rapid heartbeat, and anxiety.

3. Sleep Disorders

Conditions like obstructive sleep apnea (OSA) — where breathing pauses during sleep — can cause profound fatigue even if you believe you’re getting a full night’s rest. Insomnia, restless leg syndrome, or simply poor sleep hygiene can also contribute.

4. Depression and Anxiety

Mental health is deeply intertwined with energy levels. Fatigue is often one of the earliest or most pronounced symptoms of depression. Anxiety can also be exhausting due to chronic hyperarousal or poor sleep. These are medical conditions and deserve compassionate, evidence-based care.

5. Chronic Infections

Mononucleosis (especially in younger patients), hepatitis, HIV, or even a lingering viral infection like COVID-19 can lead to ongoing fatigue. In some cases, post-viral fatigue syndrome or long COVID may be at play.

6. Diabetes

Uncontrolled diabetes can lead to fatigue due to high blood sugar levels, dehydration, or complications like kidney issues or nerve damage.

7. Heart Disease

If the heart isn’t pumping efficiently — as seen in congestive heart failure — fatigue can be an early symptom. This is usually accompanied by shortness of breath with exertion, leg swelling, or chest discomfort. Underlying coronary artery disease can also manifest as fatigue, typically associated with additional symptoms like exertional chest pain.

8. Vitamin Deficiencies

Aside from anemia-related nutrients, low levels of vitamin D or magnesium may contribute to fatigue in some people.

9. Hormonal Changes: Postmenopausal Fatigue and Low Testosterone

Postmenopausal fatigue is a common complaint among women in their 40s and 50s. The hormonal shifts that occur during and after menopause — particularly declining estrogen and progesterone — can disrupt sleep, mood, and energy levels. Many postmenopausal women also experience hot flashes, night sweats, and increased anxiety or depression, all of which can worsen fatigue. Addressing lifestyle factors, evaluating hormone replacement therapy (when appropriate), and screening for overlapping conditions like hypothyroidism or depression are key components of care.

Low testosterone in men can also lead to fatigue, low libido, decreased muscle mass, and depressed mood. Testosterone levels tend to decline gradually with age, but some men experience more pronounced symptoms, sometimes referred to as "andropause." We check testosterone levels in the early morning and assess whether low levels are due to primary testicular dysfunction or secondary hormonal dysregulation (such as from pituitary disease or obesity).

10. Medications

Many prescription drugs — including antihistamines, blood pressure meds, antidepressants, and even statins — can cause fatigue. We always review your medication list carefully.

11. Chronic Fatigue Syndrome (CFS) / Myalgic Encephalomyelitis (ME)

A diagnosis of exclusion, CFS/ME is characterized by profound, disabling fatigue lasting at least 6 months and not improved with rest. There may be associated cognitive impairment (“brain fog”) and post-exertional malaise.

The Medical Workup: What to Expect

When you visit your primary care provider with a complaint of fatigue, here’s how we typically proceed:

1. Detailed History

This is the most important part. We ask about:

• Onset and duration of fatigue

• Lifestyle habits (diet, sleep, caffeine, alcohol)

• Stressors at work or home

• Mental health

• Any new medications or recent infections

• Menstrual history (for women)

2. Physical Exam

We look for signs like pale skin (anemia), enlarged thyroid (thyroid disease), heart murmurs (cardiac issues), or swelling (heart/kidney problems). A neurological exam may be done if brain fog or weakness is reported.

3. Laboratory Testing

Initial bloodwork often includes:

• Complete Blood Count (CBC) – screens for anemia or infection

• Thyroid Stimulating Hormone (TSH) – checks thyroid function

• Basic Metabolic Panel (BMP) – looks at kidney function and electrolytes

• Liver Function Tests (LFTs) – evaluates liver concerns

• Hemoglobin A1c – screens for diabetes

• Vitamin B12 and Folate levels

• Ferritin and Iron studies – for iron deficiency

• Vitamin D level – depending on symptoms

• C-reactive protein (CRP) or ESR – for concern for underlying inflammatory process

Depending on symptoms and risk factors, we might also test for:

• HIV

• Hepatitis B and C

• Epstein-Barr virus (mononucleosis)

• Testosterone (in men)

• Pregnancy (in women of childbearing age)

4. Additional Testing

If sleep apnea is suspected, we may order a sleep study. If depression or anxiety is likely, we may use validated screening tools and recommend mental health follow-up. If cardiac issues are suspected, we might order an EKG or refer for an echocardiogram.

When No Cause is Found

Sometimes, after a thorough workup, the tests are all normal. This doesn’t mean your fatigue isn’t real. In such cases, we may explore:

• Lifestyle factors: Inadequate sleep, poor nutrition, lack of exercise, or chronic stress

• Subclinical mood disorders

• Post-viral or idiopathic fatigue

• Burnout

Treatment may then focus on sleep hygiene, gradual exercise (like walking or yoga), therapy, stress management techniques, and cognitive behavioral therapy (CBT), especially if fatigue becomes chronic.

When to See Your Doctor

You should book an appointment if:

• Fatigue lasts longer than 2–3 weeks

• It interferes with your daily activities

• You have additional symptoms like weight loss, fever, night sweats, or significant mood changes

• You snore loudly or gasp during sleep

• You feel dizzy, weak, or short of breath

• You are concerned and want to be evaluated

Final Thoughts

Fatigue is one of the more common — and often one of the most frustrating — symptoms we deal with in primary care. The good news is that in many cases, we can find a treatable cause. And even when we don’t, there are still effective strategies to help manage it.

If you’re feeling persistently tired, don’t brush it off. Your body is trying to tell you something — and we’re here to listen.

Florida Direct Primary Care in St. Augustine

Dr. Bryant Wilson is a board certified internal medicine physician at Florida Direct Primary Care who develops individualized treatment plans that promote overall health and wellness, tailored to each patient’s unique health needs and goals. If you’re in the St. Augustine area and looking for a primary care doctor, contact us to learn more about our practice. Visit FloridaDPC.com, email us at info@FloridaDPC.com, or call 904-650-2882.

This web site is provided for educational and informational purposes only and does not constitute the provision of medical advice or professional services. The information provided should not be used for diagnosing or treating individual health problems or diseases. Those seeking medical advice should consult with a licensed physician.

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