SerpApi.Org
Medically reviewed by Erika Prouty, PharmD
Key Takeaways
- Vitamin B12 is generally safe, but rare reactions like allergies or skin flare-ups can occur.
- Serious side effects are uncommon, but high-dose treatment for deficiency can occasionally cause low potassium levels.
- Certain medications may lower B12 levels, so supplements may be needed under a healthcare provider’s guidance.
Vitamin B12 supplements are generally safe, but rare side effects like allergic reactions, acne, and low potassium levels can occur. Understanding these risks ensures you can make informed decisions about your health.
1. Allergic Reactions
Allergic reactions are a rare but serious side effect that can happen with any medication or vitamin. These reactions can vary from mild to severe and even be life-threatening.
Severe reactions mostly occur with injectable forms of vitamin B12 rather than daily oral supplements. Seek medical attention immediately if you experience symptoms like hives, difficulty breathing or swallowing, or swelling of the face, lips, tongue, or throat.
2. Acne and Rosacea
Some research has found that, in rare cases, vitamin B12 can cause acne. In one small study, 1 out of 10 participants developed acne within a week of starting vitamin B12 supplements.
There have also been isolated reports of rosacea flare-ups linked to high-dose daily B12 supplements, though these reports are rare. Interestingly, recent studies show that many people with rosacea have lower vitamin B12 levels.
If you are prone to skin conditions like acne or rosacea, talk to your healthcare provider before adding a B12 supplement to your routine.
3. Hypokalemia (Low Potassium Levels)
Hypokalemia (low potassium levels) is a rare side effect that can happen when vitamin B12 is used to treat a severe deficiency.
Vitamin B12 helps the body make new red blood cells. However, when the body begins producing new red blood cells rapidly, potassium levels can drop. This usually happens only in people who had very low vitamin B12 levels before starting B12 supplementation and who are receiving higher-dose treatment, such as injections, rather than daily supplements.
Symptoms of low potassium may include:
- Muscle weakness
- Constipation
- Fatigue
- Irregular heartbeat
If you are being treated for a vitamin B12 deficiency, your healthcare provider may monitor your potassium levels.
Who Should Not Take B12 Supplements
Vitamin B12 supplements are considered safe, even at high doses. However, it's always a good idea to check with your healthcare provider before adding any new vitamin or supplement to your routine.
Be sure to mention if you have ever had an allergic reaction to vitamin B12, cyanocobalamin, or cobalt, or if you have a rare inherited condition called Leber hereditary optic neuropathy (LHON).
What Medications May Cause a Deficiency?
Some drugs—including prescription and over-the-counter drugs—may cause you to have low B12 levels in your body, especially when taken for a long time.
If you are taking any of these drugs, your healthcare provider may routinely monitor your levels and recommend a supplement if your levels are too low:
- Metformin, which is commonly prescribed to people with diabetes to help manage blood sugar levels.
- Drugs used to control acid reflux and certain gastrointestinal conditions, such as Prilosec (omeprazole), Nexium (esomeprazole), Prevacid (lansoprazole), Pepcid (famotidine), or Tagamet (cimetidine).
Read the original article on Verywell Health
