5 Factors Doctors Check Before GLP-1 Use

Q: Are GLP-1 medications safe to use during pregnancy or breastfeeding?

No, GLP-1 medications are not suitable for use during pregnancy or breastfeeding . These medications could carry potential risks to the baby, and their safety in such situations has not been confirmed. If you're pregnant, planning to have a baby, or currently breastfeeding, make sure to consult your doctor about other treatment options that may be safer for you and your child.

GLP-1 medications are prescribed for managing type 2 diabetes and obesity, but they aren't suitable for everyone. Doctors evaluate five key factors to ensure safety and effectiveness:

BMI and Weight: Eligibility depends on BMI thresholds. In Singapore, obesity is defined at a BMI of ≥27.5 kg/m², with lower thresholds (≥23 kg/m²) for those with related health issues like diabetes or hypertension.
Medical History: Conditions like thyroid cancer, pancreatitis, or gastroparesis can disqualify you. Kidney function and risks of diabetic retinopathy are also assessed.
Current Medications: Drug interactions, especially with insulin or sulfonylureas, are reviewed. Some GLP-1 drugs can affect oral contraceptives or medications requiring precise absorption timing.
Lifestyle and Readiness: Doctors check if you've tried diet and exercise and assess your commitment to long-term healthy habits, as these treatments work best with lifestyle changes.
Pregnancy and Family Planning: GLP-1 medications aren't safe during pregnancy or breastfeeding. Women planning to conceive must stop the medication at least two months in advance.

In Singapore, these medications are prescription-only, ensuring proper medical oversight. Providers like Trimly offer telehealth services starting from $350+ monthly, including consultations and medication delivery.

5 Medical Factors Doctors Evaluate Before Prescribing GLP-1 Medications

GLP-1 Medications for Weight Loss – FAQs Answered by a Primary Care Provider

1. Body Mass Index (BMI) and Weight Status

BMI plays a key role in determining eligibility for GLP-1 treatment and ensuring its safe use. Doctors start by calculating your BMI to see if you meet the treatment criteria. In Singapore, GLP-1 medications are typically approved for individuals with a BMI of 30 kg/m² or higher. However, if your BMI falls between 27 kg/m² and 29.9 kg/m², you may still qualify if you have at least one weight-related health condition, such as hypertension, type 2 diabetes, high cholesterol, or obstructive sleep apnoea.

In Singapore, BMI thresholds differ slightly due to ethnic-specific metabolic factors. Asian populations tend to face higher metabolic risks at lower BMIs. For this reason, obesity in Singapore is defined as a BMI of 27.5 kg/m², with certain specialised programmes lowering the threshold to 23 kg/m² if a weight-related condition is present.

Classification	International BMI (kg/m²)	Asian/Singapore BMI (kg/m²)
Healthy/Normal	18.5 – 24.9	18.5 – 22.9
Overweight/Pre-obese	25.0 – 29.9	23.0 – 27.4
Obese	≥ 30.0	≥ 27.5

"It is well known that metabolic complications associated with excess weight occur at lower BMI thresholds in Asian populations than Western populations. For example, countries like Japan and Korea define obesity at BMI cut-offs of 25, while Singapore defines it at 27.5."
– Dr. Sue-Anne Toh, Co-founder and Endocrinologist, Novi Health

Doctors also consider obesity-related complications, such as heart failure, liver fibrosis, and cardiovascular disease, which may justify treatment even if your BMI is slightly below the typical threshold. In Singapore, approximately 20.7% of residents were in the high-risk BMI category (≥ 27.5 kg/m²) as of 2019–2020. Obesity rates have also climbed significantly, rising from 6.9% in 2004 to 11.6% in 2022.

2. Medical History and Pre-existing Conditions

After evaluating your BMI, the next step in personalising GLP-1 therapy is a thorough review of your medical history. This helps doctors identify any conditions that could increase the risks associated with treatment.

One important area of focus is your endocrine, pancreatic, and gastrointestinal history, as these can significantly influence the safety and effectiveness of GLP-1 medications.

Thyroid and Endocrine Concerns

If you or your family have a history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN2), GLP-1 medications are typically avoided. According to Dr. Kathryn Horton, an Internal Medicine Physician:

"Patients with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 (MEN2), Type 1 diabetes, or diabetic retinopathy should absolutely NOT take semaglutide".

It’s essential to disclose any family history of thyroid tumours or endocrine disorders during your consultation.

Pancreatic and Gastrointestinal Health

Your pancreatic and gastrointestinal health also play a significant role in determining your suitability for GLP-1 therapy. A history of pancreatitis is particularly concerning, as these medications may heighten the risk of pancreatic inflammation. Similarly, conditions like gastroparesis, which involves delayed stomach emptying, require caution. As Diana Roman, Pharm.D., notes:

"Ozempic is not recommended in patients with gastroparesis".

Doctors will also assess for issues such as gallstones or cholecystitis, as these may necessitate a more cautious approach to treatment.

Kidney Function

Kidney health is another critical consideration. While some GLP-1 medications may offer benefits for chronic kidney disease, they can also pose risks, such as acute kidney injury due to dehydration from severe vomiting or diarrhoea. If you have existing kidney problems, your doctor will closely monitor symptoms like reduced urination, swelling, or sudden weight gain .

Current Medications and Other Conditions

Your doctor will also review your current medications to identify any potential interactions, particularly those that could increase the risk of hypoglycaemia. Additionally, the therapy’s impact on diabetic retinopathy is carefully considered, as GLP-1 medications can sometimes temporarily worsen this condition. For patients already on insulin or sulfonylureas, the risk of hypoglycaemia is higher, requiring a detailed medication review .

To ensure the safest and most effective treatment plan, be prepared to discuss all current medications, chronic conditions, and any relevant family medical history during your assessment.

3. Current Medications and Drug Interactions

When prescribing GLP-1 receptor agonists, doctors carefully review your current medications to avoid complications from delayed gastric emptying. These medications slow down how quickly your stomach processes food, which can influence how your body absorbs oral drugs.

Extra caution is needed for medications managing chronic conditions. Diabetes treatments are a prime example. If you're on insulin or sulfonylureas, combining these with GLP-1s can lead to dangerously low blood sugar levels. To prevent this, your doctor will gradually adjust your doses and may recommend more frequent blood glucose monitoring.

Oral contraceptives also require attention. While most GLP-1 medications, such as semaglutide and liraglutide, don't interfere with birth control, tirzepatide can reduce the effectiveness of oral contraceptives. If you're prescribed tirzepatide, your doctor might suggest switching to a non-oral contraceptive or adding a barrier method like condoms for 4 weeks after starting the medication and for 4 weeks following any dose increase. These measures help maintain contraception effectiveness while on treatment.

Drugs with critical timing requirements are another area of focus. For instance, medications like levodopa, which have narrow therapeutic windows, may become less effective due to delayed absorption. In such cases, your doctor will closely monitor your response and may make adjustments. Similarly, if you're using oral hormone replacement therapy (HRT), switching to transdermal patches might be recommended. These bypass the digestive system entirely, avoiding any impact from slowed gastric emptying.

Additionally, your doctor will check if you're taking DPP-4 inhibitors, like sitagliptin or linagliptin. Since these work on similar pathways as GLP-1 medications, combining them is generally avoided. If surgery is on the horizon, it’s vital to inform your anaesthetist about your GLP-1 therapy. The delayed gastric emptying caused by these medications can increase the risk of aspiration during general anaesthesia.

4. Lifestyle Habits and Behavioural Readiness

Before starting GLP-1 medications, your doctor will first check if you've already given traditional weight loss methods - like adjusting your diet and increasing exercise - a fair shot. This step helps gauge how ready you are to commit to long-term lifestyle changes, as these treatments are most effective when paired with ongoing healthy habits.

During your consultation, your eating patterns and activity levels will also be closely examined. Your doctor will look at how well you can stick to a reduced-calorie diet that prioritises protein and fibre. They'll also assess how active you are physically. Research has consistently shown that combining GLP-1 treatments with lifestyle adjustments leads to greater weight loss.

"Commitment is important: Medications are part of a long-term plan that includes lifestyle support." - Dr. Linsey Gani, Endocrinologist

Another key part of this process is evaluating your readiness to build sustainable routines around nutrition, exercise, sleep, and stress management. This readiness is essential for avoiding rapid weight regain. Without maintaining healthy habits, many patients experience significant setbacks. While the appetite-suppressing effects of the medication can help you establish better eating patterns, the real success comes from actively adopting these healthier behaviours.

If, after 12 weeks of consistent use, you haven't achieved at least a 4–5% reduction in your initial body weight, your doctor might suggest stopping the medication. Building consistent habits isn't just recommended - it’s crucial for getting the most out of this treatment.

5. Pregnancy Status and Family Planning

Alongside reviewing lifestyle habits and medication history, doctors also take reproductive factors into account to ensure GLP-1 medications are used safely. Before prescribing these treatments, your doctor will confirm your pregnancy status and discuss your family planning goals. This step is crucial because animal studies have shown that medications like liraglutide and semaglutide can cause reproductive toxicity, including developmental malformations. As a result, GLP-1 medications are not recommended for individuals who are pregnant or breastfeeding.

"Individuals who are pregnant or breastfeeding, have a history of certain thyroid conditions or pancreatitis, are generally not suitable [for GLP-1 treatments]." – Dr. Linsey Gani, Endocrinologist

If you're planning to conceive, it's important to stop taking semaglutide at least two months beforehand to allow the medication to fully leave your system. While a study involving 168 pregnancies exposed to GLP-1 during the first trimester found a 2.6% rate of major birth defects - similar to rates in other groups - the data is not extensive enough to completely dismiss potential risks.

Given that nearly half of pregnancies are unplanned, this precaution becomes even more critical. If you find out you're pregnant while on GLP-1 therapy, discontinue the medication immediately and consult your doctor. For women of childbearing age who are not planning to become pregnant, effective contraception is strongly advised while undergoing GLP-1 treatment. Having an open conversation about family planning with your doctor ensures you can make well-informed decisions about your treatment and its timing.

Conclusion

When prescribing GLP-1 medications, doctors take into account five key factors to ensure the treatment is both safe and effective. These include assessing your BMI and weight status to determine clinical eligibility, reviewing your medical history to rule out contraindications like thyroid cancer, MEN 2 syndrome, or pancreatitis, checking your current medications to avoid harmful interactions, evaluating your lifestyle habits to confirm your readiness for sustainable changes, and confirming pregnancy status to eliminate risks to foetal development.

In Singapore, GLP-1 medications are strictly prescription-based, ensuring that you undergo a professional evaluation before starting treatment.

"In Singapore, these medicines are prescription-only. That means the appropriate path begins with a medical consultation, not a 'buy now' button." – Clifford Clinic

Trimly offers a telehealth service designed to provide personalised, doctor-led care. This service ensures you receive a comprehensive medical evaluation and ongoing supervision - all without the need for a clinic visit. With both oral and injectable GLP-1 options starting from $350+ per month, along with free unlimited follow-ups, Trimly delivers medication straight to your doorstep, combining convenience with professional oversight.

Always prioritise your health by obtaining GLP-1 medications through licensed providers. Avoid purchasing these medications online without a proper medical consultation.

FAQs

What are the BMI requirements for GLP-1 medication in Singapore?

In Singapore, GLP-1 medications are typically prescribed to individuals with a BMI of 30 kg/m² or higher. However, for those with a BMI of 27 kg/m² or higher, these medications might also be considered if there are weight-related health issues like type 2 diabetes, hypertension, or dyslipidaemia.

A doctor will evaluate your medical history and overall health to decide if GLP-1 therapy is appropriate for you. It’s important to seek personalised advice from a healthcare professional.

Are GLP-1 medications safe to use during pregnancy or breastfeeding?

No, GLP-1 medications are not suitable for use during pregnancy or breastfeeding. These medications could carry potential risks to the baby, and their safety in such situations has not been confirmed. If you're pregnant, planning to have a baby, or currently breastfeeding, make sure to consult your doctor about other treatment options that may be safer for you and your child.

Can GLP-1 medications be safely used with insulin or birth control pills?

GLP-1 medications can often be combined with insulin, but doctors might tweak the insulin dosage to lower the chances of hypoglycaemia. As for oral contraceptives, some research indicates that certain GLP-1 medications, such as tirzepatide, could interfere with the absorption and effectiveness of birth control pills. Because of this, doctors may suggest using additional or backup contraception methods while on these medications. Always speak with your doctor for tailored advice and regular monitoring to keep your treatment both safe and effective.