What is GLP-1? A doctor explains the difference between oral medication and injections.
食事制限をしてもなかなか続かない——そんな方の選択肢として広がっているのが、GLP-1を使った医療ダイエットです。GLP-1が体重を減らす仕組み、注射のマンジャロ・オゼンピックと飲み薬のリベルサスの違いと選び方、副作用や使えない方まで、はじめての方にもわかりやすくまとめました。
目次
"I often hear about GLP-1, but what is it?" "What's the difference between oral medication and injections?" "Which is better for me, Rybelsus or Mounjaro?" — While interest in GLP-1 receptor agonists is rapidly increasing, many also say that there are many types and the differences are hard to understand.
GLP-1 receptor agonists are drugs that work on three areas: appetite suppression, blood sugar control, and weight loss. While originally developed as a treatment for type 2 diabetes, they are now gaining attention for medical weight loss due to their powerful weight reduction effects.
In this article, a doctor from Mona Aoyama Clinic explains what GLP-1 is, the difference between oral and injectable medications, a comparison of typical drugs, side effects, and the process for online prescriptions at our clinic.
- Online consultation for GLP-1 oral medication (Rybelsus) available nationwide.
- Mounjaro (tirzepatide) also available. Same-day prescription and shipping.
- Support includes diet and exercise guidance.
What is GLP-1?
GLP-1 (Glucagon-like peptide-1) is a hormone secreted from the intestines after eating. It lowers blood sugar by promoting insulin secretion, suppressing glucagon, and slowing gastric emptying, and also has the effect of acting on the brain's appetite center to prolong "satiety."
GLP-1 receptor agonists are drugs that mimic the action of GLP-1, designed to be broken down slowly in the body and maintain their effects for a longer period.
| Main Actions of GLP-1 | Effect on Diet |
|---|---|
| Promotes insulin secretion | Suppresses rapid blood sugar spikes, reduces fat accumulation |
| Slows gastric emptying | Satiety after meals lasts longer, prevents overeating |
| Acts on the brain's appetite center | Reduces appetite itself. Food intake naturally decreases |
| Weight loss effect | Some drugs confirmed to cause ≥5-15% weight loss in clinical trials |
Oral (Pill) vs. Injection — What's the Difference?
| Comparison Item | Oral Medication (Rybelsus) | Injection (Mounjaro, Ozempic, etc.) |
|---|---|---|
| Administration Method | One tablet daily, taken immediately after waking | Weekly self-injection (subcutaneous injection) |
| Needle Resistance | ◎ No needle needed | △ Requires self-injection (thin needle, minimal pain) |
| Restrictions on Intake | △ Immediately after waking, with water only, no food/drink for 30 min | ◎ Few restrictions |
| Weight Loss Effect | ○ Approx. 3-5% (depending on dosage) | ◎ Approx. 10-20% (for Mounjaro) |
| Absorption Rate | △ Low absorption rate orally (approx. 1%) | ◎ High absorption rate subcutaneously |
| Cost | ○ Relatively affordable | △ Slightly higher |
| Recommended For | Those who dislike needles, first-time users, those seeking gradual effects | Those seeking stronger effects, those who prefer weekly management |
💡 There is no single "correct" choice. Rybelsus (oral medication) is a good starting point for those who dislike needles or are trying GLP-1 for the first time, while Mounjaro (injection) is more suitable for those seeking stronger weight loss effects. Both are available at our clinic.
Comparison of Representative GLP-1 Drugs
| Drug Name | Type | Active Ingredient | Frequency of Administration | Estimated Weight Loss Effect | Available at Our Clinic |
|---|---|---|---|---|---|
| Rybelsus | Oral medication | Semaglutide | Once daily | Approx. 3-5% | ✅ Online prescription |
| Mounjaro | Injection | Tirzepatide (GLP-1 + GIP) | Once weekly | Approx. 15-20% | ✅ Online prescription |
| Ozempic | Injection | Semaglutide | Once weekly | Approx. 10-15% | To be confirmed |
| Victoza | Injection | Liraglutide | Once daily | Approx. 5-8% | To be confirmed |
Mounjaro (tirzepatide) is a "dual agonist" that acts on both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors, and is one of the drugs with the strongest weight loss effect confirmed to date.
Side Effects of GLP-1
| Side Effect | Frequency | Management |
|---|---|---|
| Nausea/Vomiting | Most common (especially early on) | Start with a small dose and gradually increase. Reduce food intake. |
| Diarrhea/Constipation | Relatively common | Increase fluid and fiber intake. Often subsides within a few weeks. |
| Loss of Appetite | Common (also a treatment goal) | Be careful about meal content to avoid nutritional deficiencies. |
| Headache/Fatigue | Rare | Usually temporary. Consult a doctor if symptoms are severe. |
| Hypoglycemia | Rare when used alone | Caution when used with other diabetes medications. |
⚠️ Do not use if you have a history of pancreatitis or gallbladder disease, are pregnant, or breastfeeding. Please inform us of your medical history during the pre-prescription consultation.
Our Clinic's Prescription Process
- Online Medical QuestionnaireEnter your height, weight, medical history, current medications, and diet goals.
- Doctor's Review & ConsultationThe doctor will assess eligibility for prescription based on the questionnaire. We will propose the type and dosage of medication.
- Prescription & PaymentSame-day shipping for payments made by 4 PM.
- Start Medication & Follow-upInstructions for use and precautions will be provided. Follow-up support via LINE for progress.
Frequently Asked Questions
Rybelsus (oral medication) is recommended for those who dislike needles or want to try it out first. Mounjaro is suitable for those seeking stronger weight loss effects or who prefer weekly management. During the consultation, we can suggest the best option for you based on your target weight and lifestyle.
Many people experience changes in appetite within 1-2 weeks, and changes in weight begin to appear in 1-2 months. A weight loss of about 5% can be expected with 3-6 months of continuous use. Individual results may vary.
There is a risk of rebound after stopping the medication. While taking the medication, it is key to establish healthy eating and exercise habits for long-term maintenance. Our clinic also offers advice on lifestyle habits.
Prescriptions for medical diet purposes are out-of-pocket (not covered by insurance). While treatment for type 2 diabetes may be covered by insurance, our diet prescriptions are self-pay.
Related Columns
A Doctor Explains Rybelsus (Semaglutide Oral Medication): Effects, How to Take, and Side Effects Mounjaro (Tirzepatide): Effects, Side Effects, and Who It's For Want to Lose Weight by Summer? Comparing GLP-1 vs. Fat Dissolving Injections
Consultation Hours / Access (Online Consultation)
| Clinic Name | Mona Aoyama Clinic |
| Consultation Type | Online Consultation (Nationwide) / In-Person Consultation (Tokyo, Aoyama) |
| Location | D Building 3F, 1-10-3 Minami Aoyama, Minato-ku, Tokyo 107-0062 |
| Nearest Station | 5-minute walk from Tokyo Metro "Aoyama-itchome Station" |
| Online Consultation | 24-hour reception, same-day shipping available (for payments made by 4 PM) |
Consult Mona Aoyama Clinic for Medical Weight Loss
Rybelsus and Mounjaro prescribed online nationwide. Same-day prescription and shipping available.
