Dehydration: This is often the most common cause of lightheadedness and can be accompanied by a headache, especially if the dehydration is severe. Dehydration can lead to a decrease in blood volume, which in turn can cause a reduction in blood flow to the brain, resulting in lightheadedness and headache.

Tension Headache: Tension headaches are very common and can cause both lightheadedness and frontal headaches. They are often associated with muscle tension in the neck and scalp.
Migraine: While migraines are typically associated with more severe and unilateral headaches, some individuals may experience frontal headaches and lightheadedness as part of their migraine syndrome.
Anxiety or Panic Attack: Anxiety and panic attacks can cause lightheadedness and headaches due to hyperventilation and increased stress response.
Sinusitis: Frontal headaches can be a symptom of sinusitis, and if the infection is severe, it might lead to lightheadedness due to systemic illness.

Subarachnoid Hemorrhage: Although rare, a subarachnoid hemorrhage can present with a sudden, severe headache (often described as "the worst headache of my life") and lightheadedness. It is crucial to consider this diagnosis due to its high mortality and morbidity if not promptly treated.
Stroke or Transient Ischemic Attack (TIA): While less common, strokes or TIAs can present with sudden onset of headache and lightheadedness, among other neurological symptoms. Early recognition is critical for effective treatment.
Carbon Monoxide Poisoning: This can cause headache and lightheadedness due to the displacement of oxygen from hemoglobin, leading to tissue hypoxia. It's essential to consider this in individuals exposed to potential sources of carbon monoxide.

Temporal Arteritis: This condition, more common in older adults, involves inflammation of the blood vessels and can cause headaches and visual disturbances, potentially leading to lightheadedness.
Pituitary Apoplexy: A rare condition involving sudden hemorrhage or infarction of the pituitary gland, which can present with severe headache and potentially lightheadedness due to the acute increase in intracranial pressure.
Idiopathic Intracranial Hypertension: Characterized by increased intracranial pressure without a detectable cause, it can lead to headaches and potentially lightheadedness, although the latter is less common.