Headache and Nausea: Common Causes, Red Flags, and What to Do

Headache and nausea are a common symptom combination, and they can happen for many different reasons. In many cases the cause is benign, such as a migraine, dehydration, a viral illness, or not eating enough. But sometimes this combination can point to something more serious, especially when other warning signs are present.

If you are experiencing headache and nausea right now, try our symptom checker for a personalized assessment.

Common Causes of Headache and Nausea

Migraine

Migraine is one of the most common reasons headache and nausea happen together. Migraine pain is often throbbing or pulsating, may affect one side of the head, and can come with vomiting, light sensitivity, sound sensitivity, and visual disturbances.

Dehydration

When your body does not have enough fluid, blood volume drops and the brain can temporarily contract slightly, which can trigger a headache. Dehydration can also upset the stomach and cause nausea. This is especially common after exercise, heat exposure, diarrhea, vomiting, or long periods without drinking water.

Viral Illness or Infection

Many viral infections cause both headache and nausea. Flu, COVID, stomach viruses, and other infections can lead to generalized inflammation, fever, body aches, and stomach upset. If you also have fever, chills, sore throat, or fatigue, infection becomes more likely.

Tension Headache with Stomach Upset

A tension headache does not usually cause severe nausea, but stress, anxiety, muscle tension, and poor sleep can make you feel both head pain and stomach discomfort at the same time. Some people also clench their jaw or skip meals when stressed, which can worsen both symptoms.

Low Blood Sugar

If you go too long without eating, your blood sugar can drop and trigger headache, shakiness, nausea, irritability, sweating, and weakness. This can improve after eating a balanced snack or meal.

Medication Side Effects

Some medications can cause nausea while also contributing to headaches, especially if they affect blood pressure, hydration, or the stomach. Pain reliever overuse can also lead to rebound headaches.

Pregnancy

In early pregnancy, hormonal changes can lead to nausea and headaches. If pregnancy is possible, it is worth considering as part of the picture.

Less Common but More Serious Causes

Most cases are not emergencies, but some are. You should take headache and nausea more seriously if symptoms are sudden, severe, or different from your usual pattern.

Meningitis

Headache, nausea, fever, and neck stiffness can be a dangerous combination. Meningitis can also cause confusion, sensitivity to light, or extreme sleepiness.

Concussion or Head Injury

After hitting your head, headache and nausea can signal a concussion or more serious brain injury, especially if you also have vomiting, dizziness, confusion, or memory problems.

Increased Intracranial Pressure

A headache that is worse in the morning, worsens when lying down, or comes with repeated vomiting and vision changes may require urgent medical evaluation.

Stroke or Neurological Emergency

If headache and nausea come with weakness, numbness, facial droop, trouble speaking, severe dizziness, or confusion, seek emergency care immediately.

What to Watch For

Seek urgent care or emergency evaluation if you have:

• sudden severe headache
• repeated vomiting
• fainting or confusion
• weakness or numbness
• difficulty speaking
• stiff neck with fever
• vision loss or major vision changes
• symptoms after a head injury
• signs of dehydration that do not improve

What You Can Do at Home

If there are no red flags, home care may help:

• drink water or an electrolyte drink
• rest in a dark quiet room
• eat a light meal or snack if you have not eaten
• avoid alcohol and heavy greasy foods
• try over-the-counter pain relief if appropriate for you
• reduce screen exposure and get some rest

When to See a Doctor

Contact a doctor if:

• symptoms keep coming back
• headaches are becoming more frequent
• nausea prevents you from eating or drinking
• over-the-counter treatment is not helping
• symptoms are new or unusual for you
• you are pregnant and symptoms are significant

Bottom Line

Headache and nausea together are often caused by migraine, dehydration, viral illness, low blood sugar, or stress. But if symptoms are intense, unusual, or come with neurological changes, they need prompt medical attention.

Use our symptom checker to better understand what might be causing your symptoms and what next step makes sense.

This article is for educational purposes only and does not replace professional medical advice.