What the labels say, and do not say
The term brain fog does not appear in the US, European or Canadian Rybelsus® documents, and none of their side-effect lists includes memory loss or difficulty concentrating as a reaction to the tablet itself [1][2][3]. Thinking problems appear only as signs of low blood sugar.
| Document | Brain fog as a side effect | Where thinking problems appear |
|---|---|---|
| US Prescribing Information and Medication Guide [1] | Not listed | Confusion or drowsiness among low blood sugar signs |
| EU summary and package leaflet [2] | Not listed | Feeling confused, difficulty concentrating among low blood sugar signs; may reduce ability to concentrate |
| Canadian Product Monograph and patient information [3] | Not listed | Feeling anxious or confused, difficulty concentrating among low blood sugar signs |
Two large trials of oral semaglutide and thinking
The evoke and evoke+ trials were run because earlier observational studies had suggested a lower dementia risk with GLP-1 medicines. They enrolled 3,808 people aged 55 to 85 with amyloid-confirmed early Alzheimer’s disease and gave them oral semaglutide up to 14 mg once daily or placebo for up to 156 weeks [4]. The main measure was a standard dementia rating scale, the Clinical Dementia Rating Sum of Boxes, assessed after 104 weeks.
After 104 weeks, the scores had worsened by about the same amount with semaglutide as with placebo in both trials, and the trials were stopped for lack of benefit [4]. The authors reported that safety was consistent with earlier studies; adverse events of any kind were reported by 91.2% on semaglutide and 84.8% on placebo [4].
These trials were not designed to detect brain fog in people with type 2 diabetes, and the abstract does not list specific symptoms. What they do show is that, in a large group of older adults with memory problems already present, two years of oral semaglutide did not measurably worsen thinking or function compared with placebo.
A separate 2024 study of US health records from people with type 2 diabetes found that starting semaglutide was linked to a lower one-year risk of a recorded cognitive deficit than starting sitagliptin or glipizide [5]. It was observational, and its abstract does not say whether people used tablets or injections.
Why thinking can feel cloudy on Rybelsus®
- Label-supported: low blood sugar. With insulin or a sulfonylurea, Rybelsus® raises the risk of hypoglycaemia, including severe episodes [1]. The leaflets list confusion, drowsiness and difficulty concentrating among the signs [1][2][3].
- Label-supported: fluid loss. Nausea, vomiting and diarrhoea can lead to dehydration [1], and MedlinePlus lists fluid or electrolyte imbalance among causes of confusion [6].
- Studied only in animals: the tablet contains an absorption enhancer, SNAC. The US label reports that in rats, SNAC raised lactate and lowered glucose in blood and spinal fluid, with signs such as lethargy only at higher exposures [1]. No human data link SNAC to brain fog.
- Unmeasured: eating less. Decreased appetite was reported by 9.0% on 14 mg against 0.8% on placebo [3], and Cleveland Clinic lists poor nutrition among brain fog causes [7]. Whether this explains fog on the tablet has not been studied.
Common causes unrelated to the tablet
Cleveland Clinic and MedlinePlus describe many causes of foggy thinking or confusion [6][7]:
- Lack of sleep, stress, anxiety and depression.
- Diabetes itself and low blood sugar, autoimmune conditions and hormonal changes such as menopause.
- Infections, fever and recovery after COVID-19 or a long hospital stay.
- Other medicines, alcohol, and deficiencies of thiamine, niacin or vitamin B12.
What general sources suggest
Cleveland Clinic says there is no specific treatment for brain fog and suggests better sleep habits, nutritious meals, daily physical activity, short breaks during the day and writing important things down [7]. It advises telling a healthcare provider if brain fog disrupts your daily routine, such as forgetting appointments or struggling with ordinary tasks.
For sudden confusion from low blood sugar caused by a diabetes medicine, MedlinePlus says the person should have a sweet drink or snack, and that their provider should be contacted if confusion lasts longer than 10 minutes [6]. A confused person should not be left alone.
Tablet details worth knowing
Rybelsus® is taken each morning on an empty stomach, and breakfast has to wait at least 30 minutes [1]. If you also take a medicine that can lower blood sugar, that morning gap is worth discussing with your prescriber. The European leaflet asks you not to drive if you notice signs of low blood sugar, because concentration may be affected [2].
Rybelsus® and Ozempic® are registered trademarks of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.
When to get help
The signs and contact information below come from this article’s sourced guidance.
Emergency
- Confusion that comes on suddenly in someone with diabetes
Contact: Emergency services
MedlinePlus [6]
- Sudden confusion with cold or clammy skin, fast pulse, dizziness, headache or fever
Contact: Emergency services
MedlinePlus [6]
- Unconsciousness, seizures, or severe low blood sugar that needs help from another person
Contact: Emergency services
MedlinePlus [8]
Today
- Confusion from low blood sugar that lasts more than 10 minutes after a sweet drink or snack
Contact: Your provider
MedlinePlus [6]
- Foggy thinking with sweating, shakiness or hunger while on insulin or a sulfonylurea
Contact: Treat low blood sugar as taught, then tell your prescriber
Rybelsus® Medication Guide [1]