Stomach symptoms while traveling in Japan can mean many different things: heartburn, acid reflux, stomach heaviness, mukamuka, diarrhea, constipation, bloating, nausea, or cramping abdominal pain.
Quick answer: choose by symptom first, not by brand name or package design. A Japanese stomach medicine for acid reflux is different from a product for diarrhea, constipation, motion sickness nausea, or abdominal cramps.
Before buying, check the active ingredient, age limit, dose, warnings, and whether pharmacist or registered seller confirmation is needed. If you are not sure, show your symptoms and other medicines to pharmacy staff.
If you have strong chest pain, severe or sudden abdominal pain, black stool, bloody stool, vomiting blood, repeated vomiting, dehydration, difficulty swallowing, unexplained weight loss, pregnancy, or symptoms that do not improve, consider medical care instead of trying multiple OTC products.
For general OTC buying rules, see: Drugstore Basics in Japan
- Quick Symptom Guide
- 1. Start With the Symptom, Then the Ingredient
- 2. Acid Symptoms: Antacid, H2 Blocker, or PPI?
- 3. Diarrhea: Do Not Only Think “Stop It”
- 4. Constipation, Bloating, and Cramps
- 5. Nausea: Motion Sickness vs Unexplained Vomiting
- Quick Pharmacy Phrases
- When to Choose Medical Care
- FAQ
- Related Guides
- References
Quick Symptom Guide
| Main symptom | Japanese words you may see or say | Ingredient or product clues | Useful guide |
|---|---|---|---|
| Heartburn, acid reflux, sour burps | 胸やけ, 胃酸が上がる | Antacids, famotidine, PPI-type products | Antacid vs H2 Blocker vs PPI in Japan |
| Stomach heaviness after eating | 胃もたれ, むかむか, 消化不良 | Digestive enzymes, herbal stomachics, mucosal protectants | This article |
| Diarrhea | 下痢, 整腸剤, 下痢止め | Lactic acid bacteria, adsorbents, astringents, loperamide | Oral Rehydration Products in Japan |
| Constipation or bloating | 便秘, お腹の張り | Magnesium oxide, senna/sennosides, bisacodyl, sodium picosulfate, dimethicone | This article |
| Motion sickness nausea | 乗り物酔い, 吐き気 | Meclizine, scopolamine, diphenhydramine-type ingredients | Travelmin vs Aneron in Japan |
| Cramping or squeezing abdominal pain | 差し込むような腹痛 | Antispasmodic ingredients | Ask pharmacy staff first |
| Severe or unclear abdominal pain | 強い腹痛, 急な腹痛 | Do not focus on OTC ingredients first | Consider a clinic or 119 if urgent |
1. Start With the Symptom, Then the Ingredient
The word “stomach medicine” is too broad. In Japan, you may see many products under shelves labeled 胃腸薬 (ichoyaku), 胃薬 (igusuri), 整腸剤 (intestinal regulator), 下痢止め (antidiarrheal), or 便秘薬 (constipation medicine).
Ingredient names are useful as label clues, but they are not a shopping list. The same person may need a different product depending on whether the main problem is acid, diarrhea, constipation, motion sickness, or pain.
Ask pharmacy staff before use if the medicine is for a child, older adult, pregnant or breastfeeding person, or someone with kidney disease, heart disease, glaucoma, difficulty urinating, allergies, or regular prescription medicines.
For medicine overlap checks, see: Can I Combine Japanese OTC Medicines?
2. Acid Symptoms: Antacid, H2 Blocker, or PPI?
If your main symptom is heartburn, sour burps, acid coming up, or burning around the upper stomach or chest, acid-related medicine may be relevant.
Common ingredient clues include:
- antacid ingredients such as magnesium, aluminum, calcium, or sodium bicarbonate-type ingredients
- famotidine, which is an H2 blocker
- PPI-type ingredients such as lansoprazole, omeprazole, or rabeprazole sodium
Antacids neutralize acid already present. H2 blockers reduce acid secretion. PPIs generally suppress stomach acid more strongly than H2 blockers, but they are not a general answer for every stomach symptom.
In Japan, famotidine OTC products are Class 1 OTC medicines, and current non-prescription PPI products are listed as guidance-required medicines. This means pharmacist involvement is important, and the product may not be available if a pharmacist is not available.
For a focused comparison, see: Antacid vs H2 Blocker vs PPI in Japan
3. Diarrhea: Do Not Only Think “Stop It”
For diarrhea, the key question is whether it is mild travel-related diarrhea or something that could be food poisoning or infection.
Ingredient clues you may see include:
- bifidobacteria, lactomin, lactic acid bacteria, or butyric acid bacteria
- natural aluminum silicate, smectite, or albumin tannate
- loperamide hydrochloride
Intestinal regulator products are usually aimed at supporting the intestinal environment. Some antidiarrheal products try to absorb or reduce stool looseness. Loperamide slows intestinal movement and should not be chosen casually if infection or food poisoning is possible.
Ask pharmacy staff or consider medical care if diarrhea comes with fever, repeated vomiting, blood or mucus in stool, strong abdominal pain, dehydration, or several people becoming sick after the same meal.
Fluids matter. For drink, jelly, and powder options, see: Which Oral Rehydration Product Should I Buy in Japan?
4. Constipation, Bloating, and Cramps
Constipation medicine, gas medicine, and cramp medicine are different categories.
Ingredient clues you may see include:
- magnesium oxide
- senna, sennosides, bisacodyl, or sodium picosulfate
- dimethylpolysiloxane, also called dimethicone
- antispasmodic or anticholinergic ingredients such as scopolamine butylbromide or Scopolia extract
Magnesium oxide is a common osmotic or saline-type laxative ingredient, but people with kidney disease or dialysis treatment should ask before using it. Stimulant laxatives such as senna, sennosides, bisacodyl, or sodium picosulfate may cause cramping or diarrhea and should not be used repeatedly without advice.
Dimethicone is for gas-related fullness or bloating. Antispasmodic ingredients may be used for cramps, but they are not a default choice for all abdominal pain. Be careful if you have glaucoma, difficulty urinating, heart disease, are elderly, or take other medicines with similar effects.
5. Nausea: Motion Sickness vs Unexplained Vomiting
OTC nausea products in Japanese drugstores are often motion sickness medicines.
Ingredient clues may include meclizine, scopolamine, diphenhydramine salicylate, or other antihistamine-type ingredients. These can cause drowsiness, dry mouth, blurred vision, or difficulty urinating.
If nausea clearly happens during a bus, boat, car, train, or flight, motion sickness medicine may be worth asking about. If vomiting is repeated, severe, unexplained, linked with fever or abdominal pain, or you cannot keep fluids down, consider medical care.
For product-style comparison, see: Travelmin vs Aneron in Japan
Quick Pharmacy Phrases
You can show these at a Japanese pharmacy.
| English meaning | Japanese to show |
|---|---|
| I have stomach or digestive symptoms. | 胃腸の症状があります。 |
| I have heartburn or acid reflux. | 胸やけや胃酸が上がる感じがあります。 |
| My stomach feels heavy after eating. | 食後に胃もたれがあります。 |
| I feel nauseous or mukamuka. | 吐き気があります／胃がむかむかします。 |
| I have diarrhea. | 下痢があります。 |
| I have constipation or bloating. | 便秘またはお腹の張りがあります。 |
| I have cramping abdominal pain. | 差し込むような腹痛があります。 |
| I ate something suspicious. | 食中毒が心配な食事をしました。 |
| I already took this medicine. | すでにこの薬を飲みました。 |
| Can I use this with my other medicines? | ほかに飲んでいる薬と一緒に使えますか？ |
| Should I see a doctor instead? | 市販薬ではなく、受診した方がよいですか？ |
For a broader phrase card, see: Show This at a Japanese Pharmacy
When to Choose Medical Care
Do not keep switching OTC stomach products if symptoms are severe, unusual, worsening, or not improving.
Seek medical care promptly, or call 119 in Japan if urgent, for:
- strong chest pain, chest pressure, shortness of breath, cold sweat, faintness, or pain spreading to the arm, shoulder, back, jaw, or neck
- severe, sudden, or worsening abdominal pain
- black stool, bloody stool, vomiting blood, or vomit that looks like coffee grounds
- repeated vomiting, inability to keep fluids down, or dehydration signs
- difficulty swallowing, unexplained weight loss, or loss of appetite
- high fever, severe diarrhea, or suspected food poisoning
- a hard or swollen abdomen, inability to pass stool or gas, or severe constipation
- pregnancy, young child, older adult, serious chronic disease, or recent surgery
For care options, see: How to See a Doctor in Japan as a Traveler
FAQ
Can I buy stomach medicine at a Japanese drugstore?
Yes. Many Japanese drugstores sell OTC stomach and digestive medicines. Some products may require pharmacist or registered seller confirmation, and some symptoms are better handled by a clinic.
What does mukamuka mean?
Mukamuka usually means a queasy, nauseous, or unsettled stomach feeling. It is not always acid reflux, so explain whether you also have heartburn, vomiting, diarrhea, or abdominal pain.
Can I combine different stomach medicines?
Do not combine several stomach medicines, antidiarrheals, laxatives, or pain relievers on your own. Japanese OTC products often contain multiple ingredients. Ask staff to check for overlap.
When is stomach pain not a drugstore problem?
Severe, sudden, worsening, repeated, or unclear abdominal pain should not be treated as a simple OTC medicine problem, especially with fever, vomiting, blood in stool, black stool, dehydration, chest pain, or pregnancy.
Related Guides
- Drugstore Basics in Japan
- Antacid vs H2 Blocker vs PPI in Japan
- Heartburn Medicine in Japan
- Which Oral Rehydration Product Should I Buy in Japan?
- Travelmin vs Aneron in Japan
- Can I Combine Japanese OTC Medicines?
- How to See a Doctor in Japan as a Traveler
- Emergency Numbers in Japan
References
- Ministry of Health, Labour and Welfare. Information on Japan’s medicine sales system. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/0000082514.html
- Ministry of Health, Labour and Welfare. Guidance-required medicine list. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/yoshidoiyakuhin.html
- Ministry of Health, Labour and Welfare. 2026 medicine sales system update. https://www.mhlw.go.jp/stf/web_magazine/closeup/20.html
- Pharmaceuticals and Medical Devices Agency (PMDA). OTC medicine package insert search. https://www.pmda.go.jp/PmdaSearch/otcSearch/
- Japan National Tourism Organization. Guide for when you are feeling ill in Japan. https://www.jnto.go.jp/emergency/eng/mi_guide.html
- NIDDK. Symptoms and causes of diarrhea. https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea/symptoms-causes
- NIDDK. Symptoms and causes of constipation. https://www.niddk.nih.gov/health-information/digestive-diseases/constipation/symptoms-causes
- NHS. Stomach ache. https://www.nhs.uk/symptoms/stomach-ache/
- NHS. Chest pain. https://www.nhs.uk/symptoms/chest-pain/
