giving b12 injection in arm How to Use These 4 IM Spots Safely How to Give a Vitamin

For example, those with high blood pressure, heart problems, skin conditions, blood disorders, gout and low potassium levels should use vitamin B12 with caution and may want to consider talking to a trusted health care practitioner before starting supplementation

Running out before cycle completion If your supply runs short before reaching intended cycle duration: Option 1: End cycle early

Staying in the middle third of the outer thigh minimizes this risk

Symptoms of Combined Vitamin D and Vitamin B12 Deficiency Vitamin D and B12 deficiencies can occur independently

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As to the aches and pains, breathlessness etc, this could be due to B12 needing potassium to build RBC, so I would check out low potassium symptoms and eat a banana or maybe two until you have fathomed it out