What blood tests should I request?

A complete blood count (CBC), iron studies (ferritin), thyroid function (TSH), fasting glucose, and vitamin B12 cover the most common causes.

Fatigue and Dizziness Together: What Your Body Is Telling You

Important Disclaimer

This guide is for informational purposes and does not replace professional medical advice. If you are experiencing a medical emergency, call 911 or your local emergency services immediately.

Overview

Fatigue and dizziness together often indicate that your body's oxygen delivery or energy systems are compromised. The most common culprits are anemia, dehydration, blood sugar fluctuations, and blood pressure irregularities.

Possible Causes

Iron-Deficiency Anemia

common

Low hemoglobin reduces oxygen delivery to the brain, causing both fatigue and lightheadedness.

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Dehydration

common

Reduced blood volume decreases blood pressure, causing dizziness, while cellular dehydration produces fatigue.

Hypoglycemia

less-common

Low blood sugar deprives the brain of its primary fuel, causing both symptoms simultaneously.

Hypothyroidism

less-common

An underactive thyroid slows metabolism, producing profound fatigue and orthostatic dizziness.

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When It Is Serious

Seek evaluation if accompanied by rapid heart rate, fainting, chest pain, sudden severe headache, or progressive worsening over days.

When It's Likely Benign

Occurring after skipping meals, during hot weather, or after intense exercise is usually related to dehydration or blood sugar and resolves with fluids and food.

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Frequently Asked Questions

Related Resources

Fatigue Guide Dizziness Guide

Medically Reviewed for Accuracy

Medical Advisory Board

•Last reviewed: March 20, 2026

Content is aligned with established clinical guidelines from authoritative medical institutions, including MedlinePlus (U.S. National Library of Medicine), the CDC, the NIH, and the NHS. All content is reviewed by our medical advisory board for accuracy and safety.