Fatigue and Nausea: Common Causes, Warning Signs, and What to Do

Fatigue and nausea are common symptoms that can happen together for many different reasons. In many cases the cause is something temporary, such as a viral illness, dehydration, stress, lack of sleep, or not eating enough. But sometimes the combination can point to pregnancy, anemia, thyroid problems, medication side effects, or another medical issue that deserves attention.

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

Common Causes of Fatigue and Nausea

Viral Illness

Many viral infections cause both nausea and low energy. Flu, COVID, stomach viruses, and other infections can leave you exhausted, achy, and unable to eat normally.

Dehydration

Dehydration can make you feel weak, tired, lightheaded, and nauseated. If you have also had vomiting, diarrhea, heat exposure, or low fluid intake, dehydration becomes even more likely.

Poor Sleep and Stress

Lack of sleep and chronic stress can upset the stomach while also draining your energy. Anxiety can also reduce appetite and create a cycle of nausea and exhaustion.

Low Blood Sugar

If you have not eaten enough, low blood sugar can lead to weakness, fatigue, shakiness, nausea, sweating, and dizziness. This often improves after a snack or meal.

Pregnancy

Early pregnancy is a very common cause of fatigue and nausea. Hormonal changes can make both symptoms appear together, especially in the first trimester.

Medication Side Effects

Some medications can cause stomach upset and fatigue at the same time, including certain antibiotics, antidepressants, blood pressure medications, and pain medicines.

Anemia

Anemia can cause tiredness, weakness, dizziness, and sometimes nausea, especially if your body is under stress or if another illness is happening at the same time.

More Serious Possibilities

Most cases are not emergencies, but some deserve prompt evaluation.

Significant Infection

If nausea and fatigue come with high fever, dehydration, severe weakness, shortness of breath, or confusion, a more serious infection may be involved.

Liver or Gallbladder Problems

Fatigue and nausea, especially if combined with abdominal pain, jaundice, dark urine, or vomiting, may need urgent medical evaluation.

Severe Dehydration

If you cannot keep fluids down or feel faint, you may need urgent treatment.

Red Flags

Get medical help urgently if you have:

• severe dehydration
• fainting or near-fainting
• chest pain
• shortness of breath
• black stools or vomiting blood
• severe abdominal pain
• confusion
• rapidly worsening weakness

What You Can Do at Home

If there are no red flags, it may help to:

• sip water or an electrolyte drink
• eat bland foods in small amounts
• get extra rest
• avoid alcohol and greasy foods
• avoid standing up quickly if you feel weak
• consider whether a new medicine may be contributing

When to See a Doctor

See a doctor if:

• symptoms last more than several days
• you cannot keep food or fluids down
• symptoms keep coming back
• you suspect anemia, pregnancy, or thyroid problems
• fatigue is significantly affecting daily life

Bottom Line

Fatigue and nausea together are often caused by viral illness, dehydration, stress, pregnancy, low blood sugar, or medication side effects. But ongoing or severe symptoms should not be ignored, especially if you also have dehydration, pain, or signs of bleeding.

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.