What is a GLP-1?

What is a GLP-1? Who is it for? What do you need to know about it before you speak to your doctor? Read on for the answers!

We know that many of our community members have questions about GLP-1s, so we asked endocrinologist Prof. Peter Raubenheimer to answer them all.

What are GLP-1 agonists?

GLP-1 agonists are a group of medications that help to manage blood sugar in people with Type 2 diabetes, some of which can be used to treat obesity even in people who do not have diabetes. 

There are a few other names used for these medications:

• Incretin mimetics
• GLP-1 analogues
• GLP-1 receptor agonists
• Glucagon-like peptide-1 agonists
• Some just call them GLP-1’s.

List of GLP-1 agonists

GLP-1 agonist medications currently available in South Africa include: 

• Dulaglutide (Trulicity®)
• Exenatide (Byetta®)
• Liraglutide ( Giliptra®, Victoza®, Saxenda®)
• Semaglutide (Ozempic®)
• Lixisenatide: Brand name Soliqua.
• Tirzepatide (Mounjaro®) – Tirzepatide is a dual agonist that targets both GIP and GLP-1 receptors. It belongs to a new class, distinct from GLP-1 receptor agonists.

Some medications combine a GLP-1 receptor agonist with insulin in a single daily injection. These are used mainly in people with Type 2 diabetes who need stronger blood sugar control than either medicine can provide alone. Different medications are indicated for different treatments, speak to your doctor to find out more about what works best for you.

Examples of combination medications:

Xultophy®	Insulin degludec + liraglutide
Soliqua®	Insulin glargine + lixisenatide

Here’s an in-depth look at what GLP-1s are available in South Africa.

How do GLP-1 agonists work?

GLP-1 stands for Glucagon-Like Peptide-1. It’s a natural hormone made by your body, especially in your gut, after you eat. It helps control your blood sugar and reduce your appetite.

GLP-1 plays several helpful roles:

1. Lowers blood sugar after meals: It helps your pancreas release insulin only when needed – especially after eating.
2. Slows down digestion: This means food stays in your stomach longer, which helps you feel full sooner and longer.
3. Reduces appetite: It affects the brain areas that control hunger, helping you feel less hungry.
4. Lowers glucagon: Glucagon is a hormone that raises blood sugar. GLP-1 helps keep this in check.

GLP-1 agonists work by mimicking this hormone.

What is GIP?

GIP is glucose-dependant insulinotropic polypeptide, also known as gastric inhibitory polypeptide. It is a hormone that stimulates the release of insulin into the bloodstream, once it registers food in the body, to control blood sugar levels after meals. When you have Type 2 diabetes, the release of the GIP hormone is less efficient and doesn’t work effectively.

One of the medications for managing Type 2 diabetes currently available in South Africa is Mounjaro®. Mounjaro® is a dual receptor agonist that binds to both the GLP-1 receptor and the GIP receptor.

As a result, the binding of both GLP-1 and GIP makes it possible to more effectively use insulin and better manage blood sugar levels after a meal. Together, the binding and activation of the two different receptors complement each other to regulate appetite, insulin sensitivity and insulin release.  

Who might be prescribed a GLP-1?

Doctors may prescribe a GLP-1 agonist to people who:

• Have Type 2 diabetes, especially if other medications such as metformin which are usually used first aren’t enough.
• Are overweight or have obesity, especially if they also have diabetes or other health risks (Trulicity and Mounjaro are not indicated for the treatment of overweight or obesity, however).

These medicines have not been approved for use in people with Type 1 diabetes, although researchers are currently studying the safety and effectiveness for people with Type 1.

Currently medical aids do not include GLP-1 agonists in their PMB packages of care so payment is usually for the patient’s own account. The public sector in SA also does not currently provide GLP-1 agonists. 

How are GLP-1s taken?

• Most are injections, usually once daily or once weekly.
• A newer form of semaglutide (Rybelsus®) is available as a daily tablet, but is not yet available in SA.
• Injections are given under the skin (not into muscle or veins).
• Your doctor or pharmacist will teach you how to use it safely.

What are the benefits?

• Better blood sugar control
  GLP-1 medicines can lower HbA1c levels (a marker of average blood sugar over 3 months), helping to keep blood sugar levels within a normal range.
• Weight loss
  Most people lose weight – often 5 to 15% of their body weight over time – especially with lifestyle changes.
• Heart protection
  Trulicity reduces the risk of heart attacks and strokes, especially in people with Type 2 diabetes and heart disease. (Find out more about if people with diabetes need to worry about heart health here).
• Convenient dosing
  Once-weekly injections for some GLP-1s mean fewer doses and easier routines.

What are the side effects?

Like all medications, GLP-1s can have side effects. The most common are:

• Nausea
• Vomiting
• Diarrhea
• Constipation
• Bloating or indigestion

These usually improve over time. Taking the medicine with food or starting on a low dose may help.

Serious but rare side effects:

• Pancreatitis (inflammation of the pancreas)
• Gallbladder problems
• Low blood sugar, especially if taken with insulin or sulfonylureas
• Allergic reactions
• Worsening diabetes-related retinopathy

Always talk to your doctor if you have belly pain that won’t go away, yellowing of the
skin, or signs of low blood sugar (like shakiness or confusion). Here are some common
symptoms of low blood sugar.

FAQs about GLP-1s

Q: Will I need to take GLP-1 medicine forever?
A: Not always. Some people may stop after reaching their goals, while others may need
long-term treatment or an alternative treatment. Most people will regain the weight lost
on these medications when they are stopped. Your doctor will help you decide.

Q: Can I stop my diabetes tablets if I’m on a GLP-1?
A: In some cases, GLP-1 medicines reduce the need for other diabetes medications. Never stop a medicine without asking your doctor.

Q: Are GLP-1s addictive or dangerous?
A: Not usually. They work by mimicking the body’s natural incretin hormones, and they are generally safe when used under medical supervision.

Q: Are they the same as insulin?
A: No. GLP-1s help the body release its own insulin but are not insulin. Here’s all you need to know about starting insulin with Type 2 diabetes.

Q: Can I take a GLP-1 instead of insulin?
A: If you have Type 2 diabetes, you may be able to – after you discuss this with your doctor. Once diabetes needs treatment with an injection, a GLP-1 is an option instead of insulin injections, but initiation of insulin therapy may still be clinically indicated or required. However GLP-1s are not currently funded in the South African healthcare setting and so may not be available for that reason. There is no “best” way to manage Type 2 diabetes. Your doctor will discuss a treatment plan for you.

What do you think?

Have you tried GLP-1s? Do they work for you?

What to read next?

Type 2 diabetes and insulin: don’t be scared, here’s what you need to know: Think you might be ready for insulin? Read this to find out more.

10 Fast facts about hypoglycemia (low blood sugar): Not sure what hypos are? Here’s an explanation.

What is TEEL? A simple way to manage your diabetes: TEEL offers 4 rules for managing diabetes.

Image credit from Unsplash