Three labels, three answers
Each regulator’s document answers the question differently. The US prescribing information shows reactions that reached 5% in its pooled placebo-controlled trials and lists a short set of postmarketing reports; neither contains fatigue, asthenia or malaise. [1] The European summary of product characteristics uses frequency classes across the phase 3a trials, LEADER and spontaneous reports, and puts fatigue in the common class and malaise in the uncommon class. [2] The Canadian monograph prints every event reported by at least 1% of people in each trial, whether or not it was judged drug-related, so it shows how close the numbers sit to the comparison groups. [3]
| Source and term | Victoza® 0.6 mg | 1.2 mg | 1.8 mg | Comparison group |
|---|---|---|---|---|
| US label, Table 1 and section 6.2 [1] | Not listed | Not listed | Not listed | — |
| Canada, LEAD-2 (with metformin): fatigue [3] | 1.2% | 2.1% | 2.5% | Placebo 1.7%; glimepiride 1.2% |
| Canada, LEAD-2: asthenia (weakness) [3] | 0.8% | 0.8% | 1.2% | Placebo 0.0%; glimepiride 1.2% |
| Canada, LEAD-5 (with metformin and glimepiride): fatigue [3] | — | — | 0.4% | Placebo 0.0%; insulin glargine 0.0% |
| Canada, trial 1860 (with metformin): fatigue [3] | — | 3.2% | 4.1% | Sitagliptin 0.5% |
| Canada, trial 1842 (52 weeks, no placebo): fatigue [3] | — | — | 1.9% (with metformin); 3.7% (also with insulin detemir) | No placebo arm |
| EU SmPC, Table 1 [2] | Fatigue: common (1 in 100 to 1 in 10). Malaise: uncommon (1 in 1,000 to 1 in 100) |
Reading the numbers without over-reading them
Two things stand out. First, the Canadian figures are small and inconsistent: LEAD-2 shows a slight rise with dose but a placebo rate of 1.7%, while trial 1860 shows a clearer gap against sitagliptin, an oral tablet with no stomach-slowing effect. [3] Second, the trial with insulin detemir added to Victoza® had the highest fatigue figure, 3.7%, and no placebo group to compare with. [3] None of these rows can show cause, because the Canadian tables count events regardless of what an investigator thought caused them. [3]
Liraglutide is also sold at a higher dose, 3 mg a day, as Saxenda® for weight management. Its label reports fatigue in 7.5% of adults against 4.6% on placebo and says that tiredness, weakness, malaise, taste change and dizziness were mostly reported in the first 12 weeks, often alongside nausea, vomiting or diarrhea. [4] That is a different product, dose and population, so its numbers should not be transferred to Victoza®, but the pattern is a reasonable thing to watch for and tell your prescriber about.
When tiredness is really about blood sugar
For people with type 2 diabetes, tiredness has a second meaning. The Victoza® Medication Guide lists weakness, confusion or drowsiness, headache, hunger, sweating and shakiness among signs of low blood sugar. [1] The label says the risk is higher when Victoza® is combined with a sulfonylurea or insulin, and in patients aged 10 and older regardless of what else they take. [1] In the paediatric trial, 21.2% of young people on Victoza® had at least one reading under 54 mg/dL, with or without symptoms. [1] Canada’s patient information adds feeling sleepy, feeling weak and difficulty concentrating to the warning signs. [3]
High blood sugar can feel similar. MedlinePlus lists feeling weak or tired alongside thirst, a dry mouth, blurred vision and passing more urine. [8] When tiredness is new or unusual, a glucose reading at the time is the quickest way to tell these apart, and it is useful information for your prescriber either way.
Why it might happen
Label-supported links: digestive side effects are the main known reactions to Victoza®, and the label warns that vomiting and diarrhea can lead to dehydration and kidney problems, especially when starting and increasing the dose. [1] MedlinePlus lists listlessness, dizziness and confusion among signs of more severe dehydration. [10] Eating less because of nausea or reduced appetite, which affected 10% on 1.2 mg and 9% on 1.8 mg against 1% on placebo, may also leave less energy in the tank. [1]
Reported but not proven: an analysis of US spontaneous reports across six GLP-1 medicines, including liraglutide, flagged lethargy among its nervous system signals and found that these reports as a group often began early, about 45% within the first 30 days. These are reports, not rates, and cannot show that the medicine caused the symptom. [5]
Other causes worth ruling out
MedlinePlus describes fatigue as a lack of energy and motivation, different from drowsiness, and usually not a sign of serious disease. [6] Its list of causes is long and overlaps with type 2 diabetes care: diabetes itself, anaemia or low iron, an underactive or overactive thyroid, depression, poor sleep or sleep apnoea, kidney and heart disease, and alcohol. [6] It also names medicines that can cause drowsiness or fatigue, including blood pressure medicines, diuretics, antihistamines, sleeping pills and steroids, which many people with diabetes take alongside Victoza®. [6]
Steps the sources describe
MedlinePlus suggests regular sleep, a balanced diet with plenty of water through the day, regular exercise, ways to relax, a realistic schedule and avoiding alcohol and nicotine. It notes that caffeine and other stimulants do not treat fatigue and can make it worse when stopped, and that you should not stop or change any medicine without talking to your provider first. [6]
The Victoza® Medication Guide asks you to drink fluids to lower the chance of dehydration and to talk to your provider about low blood sugar, and how to handle it, before you start. [1] The EU leaflet gives the same fluid advice for the start of treatment. [2] MedlinePlus’s liraglutide page lists tiredness among side effects to mention if it is severe or does not go away. [9]
Victoza® and Saxenda® are registered trademarks of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk A/S.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| Low blood sugar signs that do not improve after a sugary snack, or a person who becomes less alert or cannot be woken | Emergency services (911 or local number); do not drive yourself | Emergency | MedlinePlus [7] |
| Tiredness with shakiness, sweating, hunger, fast heartbeat or blurred vision | Treat as possible low blood sugar per your plan; tell your prescriber | Today | Medication Guide [1] |
| Tiredness with vomiting or diarrhea that does not stop, very dark urine or little urine | Your prescriber, the same day | Today | Medication Guide [1]; MedlinePlus [6][10] |
| Fatigue with thoughts of harming yourself | Contact your provider right away | Emergency | MedlinePlus [6] |
| Unexplained fatigue with fever, unintended weight loss or night sweats | Book an appointment | At your next appointment | MedlinePlus [6] |
| Tiredness that is severe or does not go away on Victoza® | Raise it with your prescriber | At your next appointment | MedlinePlus liraglutide [9] |
