Improper Injection Site Not All Injection Sites Are Equal Choosing the wrong injection site can lead to discomfort, complications, or even ineffective absorption of Vitamin B12
Robert Cushman, head of Health Canada's biologic and genetic therapies directorate
Consult your primary care physician (or qualified healthcare provider)

Rare: may affect up to 1 in 1,000 people Acniform and bullous eruptions (acne-like and blistery skin eruptions) Not known: frequency cannot be estimated from the available data Headache, dizziness Nausea (feeling sick), vomiting, diarrhoea Malaise (feeling unwell) Rash, itching Injection site reactions including injection site pain, injection site erythema, injection site pruritus, injection site induration, and injection site swelling (Reactions at the site of the injection) Exanthema (a widespread skin rash) Chromaturia (unusual coloured urine) Fever Hot flushes (a feeling of intense heat with sweating and rapid heartbeat) Chills (feeling of coldness accompanied by shivering) Paraesthesia (feeling of pins and needles) Tremor (tremble or shakes) Hypokalaemia (decreased potassium levels in the blood) Reactive thrombocytosis (body produces too many platelets) Reporting of side effects If you get any side effects, talk to your doctor, pharmacist or nurse

Precautions Not for Direct IV Injection Alone: Must always be used as a diluent for drugs or electrolytes
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