What are the key GLP-1 side effects summary
- GLP-1 drugs now used by around 12 percent of Americans
- Gastrointestinal issues like nausea and diarrhoea affect over one in ten users
- Blindness risk linked to liraglutide and semaglutide sparks lawsuits in the US
- Acute pancreatitis reported in 574 cases with 10 deaths in the UK
- Hair loss occurs less often but still documented in trials
The popularity of GLP-1 weight-loss drugs has seen a seismic shift in just over a year. Not long ago, they were primarily used for diabetes. But now, that’s changing.
In some markets, such as the US, they’re used by up to 12% of the population.
Such side effects have the potential to turn consumers onto natural, food-based alternatives, which provide satiety effects (feelings of fullness) like GLP-1s (albeit not to the same extent).
These alternatives, produced by companies such as Vitakey in the US and Lembas in Israel, are not associated with the same side effects.
But what sort of side-effects have GLP-1 weight-loss drugs been associated with?
While this is not an exhaustive list of all side effects, these are some of the most highly publicised, and therefore will be the most likely to drive consumers into the arms of food-based alternatives.
Gastrointestinal symptoms
The most common side effects are gastrointestinal symptoms, such as nausea, vomiting, diarrhoea and constipation. These can persist for several days and present themselves in more than one in 10 users.
These symptoms often take place due to the delay in stomach emptying, according to one study. Nausea in particular, the study suggests, is related to the direct effect of GLP-1s on the central nervous system.
However, GLP-1s used primarily for the treatment of type-2 diabetes are more frequently associated with these symptoms than GLP-1s used for weight loss.
Blindness
Blindness is one of the more serious side effects linked to GLP-1 medications.
Active ingredients in GLP-1s including liraglutide (the compound in Saxenda and Victoza) and semaglutide (used in Ozempic and Wegovy) have been linked to the increased risk of developing a condition that leads to the sudden and irreversible loss of vision.
One recent paper found a link between liraglutide and Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION), sometimes known as ‘eye stroke’, in adults with diabetes.
No causal relationship has been established between blindness and either semaglutide or liraglutide, however.
UK pop star Robbie Williams brought the issue into the public’s attention claiming that the medications were harming his eyesight – albeit not the specific GLP-1s that had been previously linked to blindness. Williams is taking Mounjaro, the active ingredient of which is tirzepatide.
The issue is far from over. Lawsuits against drug manufacturers Eli Lilly and Novo Nordisk over blindness are becoming so numerous that a panel of federal judges in the US recently announced that they would be centralised.
Acute pancreatitis
One of the most serious potential side effects that has been linked to GLP-1s is acute pancreatitis (inflamed pancreas). According to the UK’s Medicines and Healthcare products Regulatory Agency (MHRA), 574 cases of acute pancreatitis and 10 deaths have been linked to the drug. The UK government also states that pancreatitis is a risk.
According to one review, however, recent large-scale meta-analyses do not support the connection, although one study on liraglutide did show a correlation between taking the drugs and the increased risk of pancreatitis. The research suggested that any link was more to do with the degree of weight loss than the drug itself, which can lead to pancreatitis-linked conditions such as gallstones. Some conditions linked to GLP-1 use, such as hypercalcemia (too much calcium in the blood) have also been linked to pancreatitis.
It should be noted that many of the researchers of this study have spoken, taught or consulted for Eli Lilly and Novo Nordisk, key producers of GLP-1 drugs.
Hair loss
Hair loss is sometimes listed as a side-effect for some GLP-1s, such as Wegovy, affecting between one in 10 and one in 100 people. Clinical trials for Wegovy showed that 3% of patients experienced hair loss, compared with 1% on the placebo.
This hair loss is usually both temporary and mild, according to Mounjaro manufacturer Eli Lilly.
Some researchers suggest that the hair loss is not directly linked to the drugs themselves, but the rapid weight-loss they cause. Weight loss can indeed be one of the causes of hair loss.
Allergic reactions
Allergic reactions on GLP-1 weight-loss drugs have been recorded, although these are significantly less common than previous side effects.
One study recorded reactions to the drug on the skin where the patients were injected. In other patients, oral semaglutide was associated with swelling, hives, dizziness, and hypertension.
Eli Lilly and Novo Nordisk have been contacted for their response.
