With Mounjaro, many people find that side effects become milder as they keep using it. Symptoms may appear temporarily when you start or after a dose increase, but most of them can be managed. If a symptom concerns you, please don't just put up with it. Ask us on LINE.
Temporary symptoms after you start or increase your dose, such as mild nausea or a bloated stomach
Contact us on LINE
Symptoms that are hard to bear, last a long time, or keep coming back, or whenever you wonder, “Is this okay?” Even small concerns are welcome
See a doctor right away
When you have any of the symptoms listed under “Seek medical care right away”
Stomach and digestion
Nausea and vomiting
Common
Why does it happen?
It tends to occur when you start or after a dose increase, and in most cases it becomes milder over time.
What to try
To avoid dehydration, drink small amounts of fluid often
If you cannot eat at all, have some sugar, such as glucose tablet candy (e.g. ラムネ) or hard candy, to avoid low blood sugar
When you can eat again, start with jelly, then move on to foods that are easy to digest, such as udon noodles
If it has not gone away by the next day, please contact us on LINE. The doctor will decide whether to adjust your dose or pause the medication. If you cannot even drink fluids, please check “Seek medical care right away” below.
Stomach discomfort, abdominal pain, and stomachache
Common
Why does it happen?
Because your stomach moves more slowly, you may feel bloating, pressure, or mild pain in your stomach.
What to try
Limit fatty meals and spicy or strongly seasoned foods
For mild pain, it is fine to use the over-the-counter pain reliever acetaminophen (e.g. タイレノールA, カロナールA)
If it continues, please talk to us; we will consider adjusting your medication
Do not use medicines that further slow down the movement of your stomach, such as butylscopolamine (e.g. ブスコパン). If the pain is strong or continues, don't rely on pain relievers to get through it. Please check “Seek medical care right away” below.
Burping and heartburn
Common
Why does it happen?
Because food in your stomach flows back up more easily, you may have burping or heartburn.
What to try
Eat small amounts at a time
Avoid eating before going to bed
Over-the-counter stomach medicine that reduces stomach acid may give you temporary relief; avoid products that contain ingredients that slow down the movement of your stomach, such as scopolia extract (ロートエキス)
If it continues, please talk to us; we will consider adjusting your medication.
Constipation and diarrhea
Common
Why does it happen?
These can happen because of changes in the way your intestines move.
What to try
If needed, use an intestinal regulator (a medicine that helps regulate your bowels)
Fatty meals can make symptoms worse, so limit them
If you have not had a bowel movement for several days and your stomach is bloated or you are vomiting, or if you have diarrhea and cannot take in fluids, please check “Seek medical care right away” below.
Whole body
Dizziness, palpitations, and numbness (symptoms similar to low blood sugar)
Sometimes
Why does it happen?
Mounjaro on its own is not a medicine that suddenly causes low blood sugar, but when you eat much less than usual, symptoms similar to low blood sugar can appear.
What to try
Have some sugar, such as glucose tablet candy (e.g. ラムネ), hard candy, or juice that contains sugar
If it keeps happening, be sure to talk to us
If you are using other diabetes medicines at the same time, low blood sugar is more likely to occur. If you have strong cold sweats or shaking, feel confused or not fully alert, or do not get better after having sugar, seek medical care right away.
Tiredness, sleepiness, and feeling feverish
Sometimes
Why does it happen?
This may occur when you start, but in most cases it becomes milder as you continue.
What to try
Rest and don't push yourself
If it is severe, please talk to us
If symptoms are strong or last a long time, the doctor will decide whether to adjust your dose.
Thirst and needing to urinate often
Sometimes
Why does it happen?
Some people feel thirsty or need to go to the toilet more often, because they eat less and drink more fluids to make up for it.
What to try
Even if you need to urinate often, don't cut down on fluids too much
If strong thirst continues, please talk to us. If you pass almost no urine or feel unsteady, please check “Seek medical care right away” below.
Muscle pain (back, thighs, calves, etc.)
Sometimes
Why does it happen?
It may appear for a short time, but in most people it goes away on its own within 2–3 days.
What to try
If the pain is strong, it is fine to use an over-the-counter pain reliever: acetaminophen, or ibuprofen (e.g. イブ). If you cannot take in enough fluids because of nausea or diarrhea, or if you have stomach symptoms, choose acetaminophen
If the pain continues, please talk to us.
Irregular periods and bleeding between periods
Sometimes
Why does it happen?
Your periods may become irregular, for example because of hormone changes caused by weight loss.
What to try
Lose weight at a pace that is not too hard on your body
If the bleeding is heavy or continues, please seek medical care. If you might be pregnant, stop using the medicine and talk to us.
Skin, injection site, and mood
Skin problems and hair loss
Sometimes
Why does it happen?
This is thought to be caused by a temporary lack of nutrients as you eat less.
What to try
Eat protein
Get B vitamins, iron, and zinc
Eat healthy fats
Drink plenty of fluids
You may use supplements if needed.
Rash, itching, and injection-site symptoms
Sometimes
Why does it happen?
Redness, itching, or a lump may appear where you injected.
What to try
Use a different injection site each time
If your skin reacts to alcohol swabs, please talk to us
If the redness, pain, or warmth is strong, please talk to us.
Feeling low or lacking motivation
Needs attention
Why does it happen?
People who already tend to have ups and downs in mood may feel this way for a while.
What to try
Don't push yourself; please talk to us
If you keep feeling distressed, please don't just put up with it. Talk to us. If you feel that you want to die or hurt yourself, seek medical care right away or call 119.
Seek medical care right away
These symptoms are rare but need attention. If you have any of the following, do not inject your next dose, and seek medical care right away. Once things have settled down, please also let us know on LINE.
Strong abdominal pain or severe back pain that continues (it may come with nausea)
A strongly bloated abdomen and being unable to pass stool or gas (you may also vomit)
Pain in the pit of the stomach or on the right side of the abdomen, with fever; yellowing of the whites of the eyes or the skin; or dark urine
Difficulty breathing, swelling of the face or throat, or hives all over the body
Strong cold sweats or shaking, feeling confused or not fully alert, or no improvement after having sugar
Repeated vomiting or diarrhea and being unable to take in fluids, passing almost no urine, or feeling unsteady
If you have difficulty breathing or swelling of the throat, or you feel confused or not fully alert, call 119 for an ambulance without hesitation (if you cannot move on your own, ask people around you or the front desk of your accommodation for help).
Please contact us on LINE soon
You have had gallstones before, and you have abdominal symptoms
You were told at a health checkup that your liver function is abnormal
Ask us about any symptom on LINE, anytime
Messages accepted 24 hours a day (replies during business hours, Japan time, JST).
*This page is a general guide. What to do may differ depending on how strong your symptoms are, how long they last, your past illnesses, and other medicines you take. If you are worried, please don't decide on your own to just put up with it. Talk to us.