Caffeine toxicity can include symptoms like dizziness, increased heart rate, muscle twitching, confusion, hallucinations, convulsions, and sleep problems.

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Mann said he personally experienced side effects like dizziness, confusion and flashbacks from wearing early versions of smart glasses that he designed himself.

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Studies have shown that "difficult" patients tend to have nebulous, hard-to-pin-down symptoms like headache, dizziness, and fatigue, notes Kurt Kroenke, M.

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Some common side effects, like nausea, dizziness or slight fatigue, are manageable--especially if the end result is pneumonia or tuberculosis, diseases that were once deadly but now can be treated with antibiotics.

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CO2 can build up in confined spaces and high levels of CO2 can produce a variety of health effects that can affect sleep, like headaches, dizziness, restlessness, difficulty breathing, increased heart rate and sweating.

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