Caffeine (MedlinePlus, National Library of Medicine)

Tier 1: Established: peer-reviewed research or government health authority
Publisher: MedlinePlus, U.S. National Library of Medicine · Published: August 11, 2026 · Accessed: August 11, 2026

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Claims this source supports

• Too much caffeine can cause restlessness and shakiness, insomnia, headaches, dizziness, fast heart rate, dehydration, and anxiety.
• Some people are more sensitive to the effects of caffeine than others.
• Caffeine reaches its peak level in the blood within one hour of consumption, and its effects can continue for hours.
• People with sleep disorders, anxiety, arrhythmia, or high blood pressure may be more affected by caffeine.