A lack of B12 can lead to anemia (not having enough red blood cells), which causes you to feel tired and weak
Ekman R, Agren G, Heilig M, Widerlov E
Some patients experience mild side effects such as temporary redness, swelling, bruising, or tenderness at the injection site
At clinical doses under supervision, the most common side effects are mild nausea in the first week (typically resolves by day 7 to 10), injection site reactions (redness, minor swelling, localized soreness lasting 24 hours), and occasional transient fatigue or mild headache in the first few days
In a 24-week phase 2 study investigating the effects of mazdutide on Chinese participants with overweight or obesity, there is a dose response effect, with a mean weight loss of 7.2%, 10.6%, and 11.6% at 3.0 mg, 4.5 mg, and 6.0 mg, respectively, compared to 1.0% with placebo (88)