What counts as fatigue, and how often
A footnote under both adult US tables says the fatigue row combines two terms: fatigue itself and asthenia, the clinical word for a general lack of strength. [1] The EU product information also uses a grouped term and places fatigue in its “very common” band; the Canadian monograph does the same grouping. [2][3]
| Source and pool | Placebo | Wegovy® 2.4 mg | Wegovy® 7.2 mg |
|---|---|---|---|
| US Table 3: weight-reduction trials, up to 68 weeks [1] | 5% | 11% | not in these trials |
| US Table 4: higher-dose trials, 72 weeks [1] | 5% | 9% | 11% |
| US Table 5: adolescents [1] | no row | no row | — |
| EU SmPC 4.8: STEP 1–4 [2] | not given | “very common” (at least 1 in 10) | — |
| Canadian Table 4: STEP 1–3 [3] | 5.1% | 11% | — |
About twice the placebo rate, mostly early on
In both adult US pools, roughly one in twenty people on placebo reported fatigue; on Wegovy® the share was about double. [1] Unlike headache, where the medicine and placebo columns sat close together, tiredness shows a clear gap.
The US label does not say when fatigue was most frequent. The EU product information fills that in: its table marks fatigue as mainly seen during the dose-escalation period, the same footnote it gives to nausea, vomiting and diarrhoea. [2] The Canadian patient leaflet lists feeling weak or tired among very common effects and says these usually go away over time. [3] Neither gives a typical duration.
The injection is built up from 0.25 mg in four-week steps to a maintenance dose from week 17, and a prescriber may delay a step by four weeks if a dose is not tolerated. [1]
Teenagers and the trial diet
Table 5, for the adolescent trial, lists reactions reported in at least 3% of teenagers on the injection and more often than on placebo. Fatigue is not among them, so there is no teenage rate. The Medication Guide’s list of common side effects, which includes tiredness, covers adults and children aged 12 and older together. [1]
Section 12.2 explains that semaglutide decreases calorie intake, most likely by acting on appetite, and section 14.2 says trial participants on both medicine and placebo followed a reduced-calorie diet with more activity. [1] The placebo group was dieting too, which is worth remembering when comparing the columns.
Why tiredness may happen: three layers
- In the product information: fatigue is a listed reaction, about twice as frequent as on placebo and mainly seen during dose escalation. [1][2] None of the documents explains the mechanism.
- Label effects that can feel like tiredness: low-blood-pressure reactions (1.3% on Wegovy® versus 0.4% on placebo) and fainting (0.8% versus 0.2%), some linked to digestive reactions and fluid loss, more often in people also taking blood pressure medicines; and, in type 2 diabetes, low blood sugar, whose listed signs include weakness, drowsiness and confusion. [1]
- Plausible but not measured: eating less is how semaglutide reduces weight (section 12.2), and lost fluids from vomiting or diarrhoea can leave people drained. [1] The label does not tie fatigue to either, so treat this as background, not an explanation.
Other causes of fatigue
Fatigue is common and usually not due to serious disease, but MedlinePlus lists many possible causes: anaemia or low iron, depression or grief, persistent pain, sleep disorders such as insomnia or obstructive sleep apnoea, an underactive or overactive thyroid, alcohol or drug use, diabetes, heart, kidney or liver disease, infections and malnutrition. [5] Medicines such as antihistamines, blood pressure medicines, sleeping pills, steroids and water pills can also cause tiredness. [5]
MedlinePlus separates fatigue, a lack of energy and motivation, from drowsiness, the need to sleep. [5] Noting which one you feel, and whether it started with a dose step, a new medicine or a stretch of poor sleep, gives your prescriber more to work with.
What general guidance suggests
MedlinePlus suggests getting enough sleep, eating a balanced diet and drinking plenty of water through the day, exercising regularly, learning ways to relax, keeping a reasonable schedule and avoiding alcohol and drugs. It notes that stimulants such as caffeine do not treat fatigue and can make it worse when stopped, and suggests asking your provider whether any vitamins might help rather than starting them on your own. [5]
The Wegovy® label has no fatigue-specific advice. It does ask people with type 2 diabetes to talk with their provider about how to recognise and treat low blood sugar, to check blood sugar before and during treatment, and to tell their provider about all other medicines. [1] MedlinePlus lists tiredness or weakness, shakiness, sweating, hunger, headache and unclear thinking among symptoms of low blood sugar. [6]
Wegovy® is a registered trademark of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| Thoughts of harming yourself | Your provider right away, or your local emergency number | Emergency | MedlinePlus [5] |
| Weakness or drowsiness with shakiness, sweating, confusion or a fast heartbeat, if you have diabetes | Follow the low blood sugar plan from your diabetes team; emergency help if severe | Emergency | Medication Guide [1]; MedlinePlus [6] |
| Fatigue with confusion, dizziness, blurred vision or very little urine | Your provider right away | Today | MedlinePlus [5] |
| Exhaustion while vomiting or diarrhoea keep going | Your prescriber, promptly | Today | Medication Guide [1] |
| Unexplained tiredness with fever, weight loss you did not try for, night sweats, or feeling cold, dry skin and constipation | Book an appointment with your provider | At your next appointment | MedlinePlus [5] |
| Tiredness that bothers you or does not lift | Your prescriber at the next visit | At your next appointment | Medication Guide [1] |
