Blood tests to order for fatigue
If you are constantly tired despite adequate sleep, your doctor will typically order these tests to find the cause:
1. CBC (Complete Blood Count)
Checks for anaemia — the most common cause of fatigue in India. Low haemoglobin means your blood is carrying less oxygen to your muscles and brain. Even mild anaemia (Hb 10–11 g/dL) causes significant fatigue.
2. Thyroid Profile (TSH)
An underactive thyroid (hypothyroidism) is extremely common, especially in women over 30. It causes fatigue, weight gain, hair loss, constipation and feeling cold. TSH above 4.5 mIU/L suggests hypothyroidism. Treatment with levothyroxine often brings energy levels back to normal.
3. Vitamin B12
B12 deficiency causes profound fatigue, along with tingling in hands/feet and memory problems. Extremely common in Indian vegetarians. B12 below 200 pg/mL is deficient and needs treatment with supplements or injections.
4. Vitamin D
Deficiency is present in up to 80% of urban Indians. Symptoms include fatigue, muscle aches, bone pain and low mood. Vitamin D below 20 ng/mL is deficient and highly treatable with supplements.
5. Ferritin (Iron Stores)
Even without full anaemia, low ferritin (iron stores below 30 ng/mL) causes fatigue. This is especially common in women with heavy periods. Ferritin can be low when haemoglobin still appears normal — which is why ferritin must be tested separately.
6. Fasting Blood Sugar / HbA1c
Uncontrolled or undiagnosed diabetes causes fatigue because cells can't use glucose properly. Many people with Type 2 diabetes don't know they have it. A fasting sugar or HbA1c screens for this.
7. Liver Function Test (LFT)
Liver disease causes fatigue, especially fatty liver (NAFLD) which is increasingly common in India. Elevated SGPT/ALT is a common finding in people with unexplained tiredness and metabolic syndrome.
What if all tests are normal?
If all routine blood tests are normal but fatigue persists, other causes to consider include: sleep apnea (interrupted breathing during sleep), depression or anxiety, overwork and burnout, chronic fatigue syndrome (ME/CFS), or medications causing drowsiness. Discuss these possibilities with your doctor if labs are unrevealing.
Questions to ask your doctor
- Should I test all seven of these, or start with the most likely ones based on my situation?
- My B12/D/ferritin is normal — what else should we check?
- Is my fatigue possibly related to my diet, sleep quality or stress?