Fatigue / Low Energy: A Symptom-Based Clinical Approach

🚪 Introductory Case (Doorway Info)

• Patient: 45-year-old female
• Chief Complaint: “I’ve been feeling tired for the past month.”
• Vital Signs: BP 112/68, HR 72, RR 14, Temp 36.8°C, SpO₂ 98%
• Appearance: No acute distress. Vegetarian. Full-time working mother of two teens.

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🧠 How Do We Think Through This?

Fatigue is one of the most common complaints in outpatient settings—but it can be caused by anything from lifestyle stress to serious systemic disease.

👉 Let’s break it down step-by-step, starting with what not to miss.

🚨 First, Rule Out Red Flags

Before diving into a full workup, check for these serious warning signs. Each demands prompt investigation:

Red Flag	Why It Matters
Sudden or recent onset	May signal infection, heart failure, stroke, or endocrine crisis
Unintentional weight loss	Think malignancy, chronic infection, or hyperthyroidism
Night sweats / fevers	Possible lymphoma, TB, or endocarditis
Neurologic deficits	Consider CNS tumors, demyelination, or paraneoplastic syndrome
Dyspnea or chest pain	Suggests cardiopulmonary disease like CHF or anemia
Suicidal ideation / low mood	May indicate major depressive disorder needing immediate care

🗣️ Step 1: Take a Focused History

Domain	Sample Questions
Onset / Duration	“When did this start?” “Has it been getting better or worse?”
Sleep Quality	“Do you feel rested in the morning?” “Any snoring or insomnia?”
Activity Tolerance	“Have you had to cut back on work or housework?”
Menstrual History	“Are your periods heavier or more irregular than usual?”
Diet / Nutrition	“Have you changed your diet?” “Are you vegetarian or vegan?”
Psychosocial Stress	“What’s going on in your work or home life lately?”
Mental Health	“Have you felt low, anxious, or emotionally exhausted?”

📁 BATHE Technique: Background, Affect, Trouble, Handling, Empathy

🩺 Step 2: Perform a Targeted Physical Exam

System	Findings to Look For
Skin	Dryness, pallor, rashes, bruising
HEENT	Pale conjunctiva, thyroid enlargement
Cardiopulmonary	Murmurs (anemia), crackles (CHF), tachycardia
Neurologic	Weakness, delayed reflexes, cognitive slowing
Abdomen	Hepatosplenomegaly (infection, malignancy)

🧠 Step 3: Generate Differential Diagnoses

Category	Possible Diagnoses
Nutritional	Iron-deficiency anemia, B12 or folate deficiency
Endocrine	Hypothyroidism, adrenal insufficiency
Psychiatric	Depression, anxiety, burnout
Cardiopulmonary	CHF, arrhythmia, COPD
Infectious	Mononucleosis, HIV, chronic hepatitis
Autoimmune	SLE, RA, polymyalgia rheumatica
Neoplastic	Leukemia, lymphoma, paraneoplastic syndrome

🧪 Step 4: Order Initial Labs

Test	Rationale
CBC + diff	Anemia, leukemia
Ferritin, iron panel	Iron-deficiency anemia
TSH, Free T4	Hypothyroidism
Vitamin B12 / Folate	Nutritional causes
BMP, glucose	Kidney issues, diabetes
ESR / CRP	Chronic inflammation or autoimmune
PHQ-9 / GAD-7	Depression / anxiety screening

🧬 Step 5: Apply the Framework to Our Case

• Heavy menstruation
• Cold intolerance and dry skin
• Vegetarian diet
• Family history of hypothyroidism

→ Likely causes: Iron-deficiency anemia, hypothyroidism, and possibly mild depression

🧪 Role of POCUS in Fatigue / Low Energy

POCUS can rapidly identify hidden contributors, especially when labs are inconclusive.

Target	Possible Findings	Relevance
Heart (ECHO)	Low EF, effusion	CHF, myocarditis
IVC	Collapsibility or distension	Volume status
Thyroid	Goiter, inflammation	Hypothyroid state
Lung scan	B-lines, effusion	CHF, infection
Abdominal scan	Hepatosplenomegaly, mass, ascites	Malignancy, infection

💡 POCUS helps confirm or exclude serious etiologies at bedside.

Special Populations

👵 Elderly

• More likely to present with fatigue from CHF, malignancy, hypothyroidism, or polypharmacy
• Depression often presents with somatic symptoms (not sadness)

🧒 Pediatric

• Consider growth failure, sleep disorders, bullying, or nutritional gaps
• Ask about school performance and energy levels at play

🗣️ Clinical English Phrases

• “Let’s check if your tiredness is from something physical, emotional, or both.”
• “Have you been able to do your usual activities?”
• “Do you feel physically tired, sleepy, or mentally drained?”
• “Has anything in your life changed recently?”
• “Would you say you still enjoy your usual hobbies?”

📌 Clinical Pearls

• Always ask about menstruation in reproductive-age females
• Fatigue + hair loss + cold intolerance = check thyroid
• “I’m fine” doesn’t always mean fine—dig deeper
• Fatigue may be the only symptom of depression or cancer
• Labs can be normal even in serious cases—trust your clinical instincts

🔗 Related Resources

• ▶ Mock Case: Fatigue – Standard
• ▶ How to Use Clinical Reasoning