Can Mounjaro Cause Headaches?

Headaches are usually not caused by the medication itself, but by how it affects your body as it adjusts. The most common reasons include:

Dehydration

Mounjaro reduces appetite and sometimes thirst cues, which means some people unintentionally drink less water. Even mild dehydration can trigger headaches, along with dry mouth, dizziness, and fatigue. This is one of the most common, preventable causes.

Low blood sugar (hypoglycaemia)

Because Mounjaro helps improve insulin sensitivity and lower blood glucose, blood sugar may drop, especially in people with diabetes or those taking other glucose-lowering medications. Headaches from low blood sugar are often accompanied by shakiness, sweating, or irritability.

Fluctuations in blood sugar

Even if your blood sugar does not drop too low, changes in blood sugar levels can still trigger headaches. As your body adjusts to improved glucose control, these temporary fluctuations may lead to pressure-type or tension-style headaches.

Nausea and reduced food intake

If Mounjaro causes nausea or makes you feel full more quickly, you may end up eating less than usual. Skipping meals or going long periods without food can trigger headaches, either due to drops in blood sugar or hunger-related tension.

Mild fluid and electrolyte changes

Reduced appetite, vomiting or diarrhoea can alter hydration and electrolyte balance. Even small changes in sodium or potassium can contribute to headaches.

Adjustment phase during dose increases

Headaches are more likely when starting Mounjaro or increasing the dose. As your body adapts to slower gastric emptying and hormonal changes, temporary side effects, including headaches, may appear.

Sleep disruption or fatigue

Some people experience tiredness or disrupted sleep while adjusting to treatment. Poor-quality sleep is a well-known trigger for headaches and can make them feel more intense.

Stress from stomach related side effects

Nausea, bloating, or constipation can cause physical stress on the body. This tension may contribute to stress-type headaches, especially in the early weeks of treatment.

Increased sensitivity to alcohol

If you drink alcohol, Mounjaro may increase your sensitivity to dehydration and changes in blood sugar, both of which are common triggers for headaches after drinking.

Further reading: Mounjaro and alcohol

Stay well hydrated

Mounjaro can reduce your body’s natural need for fluids, which may make you drink less without realising. Regular water intake helps maintain proper fluid balance, reduces dehydration-related headaches, and supports overall wellbeing.

Carry a water bottle and sip consistently throughout the day.

Eat regular, balanced meals

Eating balanced meals that include lean protein, healthy fats, and complex carbohydrates helps keep blood sugar stable and reduces the risk of headaches caused by hunger or low glucose levels.

Avoid skipping meals

Skipping meals can lead to rapid drops in blood sugar, a common headache trigger. Even small snacks can help maintain stable glucose levels and reduce headache frequency.

Try to avoid skipping meals, particularly during dose increases or if you are experiencing nausea.

Monitor blood sugar levels

For people with diabetes, headaches can occur when blood sugar levels drop too low or change too quickly.

Regular monitoring helps you identify these changes early, reducing the risk of headaches and other symptoms such as dizziness and fatigue.

Limit or avoid alcohol

Alcohol can exacerbate dehydration and cause swings in blood sugar, both of which increase the likelihood of headaches.

This effect is also seen with other weight loss injections, such as Wegovy, so moderation or avoidance is recommended.

Increase fluids and electrolytes if experiencing vomiting or diarrhoea

Gastrointestinal side effects can lead to fluid and electrolyte loss, which may contribute to headaches.

Maintaining good hydration with water, electrolyte drinks, or clear broths can help restore balance and reduce symptoms.

Prioritise good sleep

Fatigue and poor-quality sleep are common headache triggers.

Maintaining a consistent sleep schedule, avoiding screens before bed, and creating a relaxing bedtime routine can reduce tension-type headaches.

Manage stress

Stress can contribute to tension headaches.

Gentle stretching, yoga, deep breathing exercises, or light physical activity can help relieve muscle tension and lower the risk of headaches.

Speak to a pharmacist or clinician if headaches persist

Persistent or severe headaches may indicate an underlying issue. Our team can assess your symptoms, suggest adjustments, and provide safe treatment options if needed.

Most headaches are mild and short-lived, but certain symptoms require prompt medical assessment. Contact a healthcare professional urgently if you experience:

• Severe or persistent headaches that do not improve with over-the-counter pain relief
• Headaches accompanied by blurred or double vision, confusion, or speech difficulties
• Signs of severe dehydration, such as dark urine, a very dry mouth, or feeling faint, that do not improve with fluids
• A sudden, intense headache often described as the “worst headache ever”
• A headache alongside a high fever or a stiff neck
• Always speak to your doctor or pharmacist if you are concerned about side effects, or before making any changes to your medication or dosing schedule.

• Headaches can happen on Mounjaro, but they are relatively uncommon.
  Most large trials reported headache in only a small percentage of people compared with much more frequent digestive effects.
• Higher doses may slightly increase the chance, but even at the highest doses studied, most people did not report headaches.
• Headache rates may be similar to placebo in some studies, which means factors like dehydration, hunger, or blood sugar changes often play a role.
• Headaches tend to be mild and temporary, particularly during the first few weeks or around dose increases.