At what TSH level is hypothyroidism diagnosed?

TSH above 4.5-5.0 mIU/L generally indicates hypothyroidism, though symptoms can begin in the subclinical range.

Fatigue and Weight Gain: Thyroid, Hormonal, and Metabolic Causes

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

When fatigue and weight gain co-occur without lifestyle changes, it strongly suggests a metabolic or hormonal imbalance. The thyroid gland is the most common culprit, but Cushing's syndrome, PCOS, and insulin resistance should also be considered.

Possible Causes

Hypothyroidism

common

An underactive thyroid slows metabolism, causing weight gain despite normal eating and profound fatigue.

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Depression

common

Emotional eating, reduced activity, and neurochemical changes can cause both weight gain and fatigue.

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When It Is Serious

Rapid unexplained weight gain, severe fatigue limiting daily activities, or accompanying hair loss and cold intolerance.

When It's Likely Benign

Gradual weight gain from reduced activity during a stressful period with mild fatigue.

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Frequently Asked Questions

Related Resources

Fatigue 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.