Vitamin B12 : Uses, Side Effects, Interactions & More

Why is this medication prescribed?

Vitamin B12 (Cyanocobalamin nasal gel) is used to prevent a lack of vitamin B12 that may be caused by any of the following: pernicious anemia (lack of a natural substance needed to absorb vitamin B12 from the intestine); certain diseases, infections or medications that decrease the amount of vitamin B12 absorbed from food; or a vegan diet (strict vegetarian diet that does not allow any animal products including eggs and dairy products). Lack of vitamin B12 can cause anemia (condition in which the red blood cells do not bring enough oxygen to the organs) and permanent damage to the nerves. This anemia must be treated with vitamin B12 injections. After the red blood cells have returned to normal, Vitamin B12 can be used to stop anemia and other symptoms of lack of vitamin B12 from coming back. Vitamin B12 is also used to supply extra vitamin B12 to people who need unusually large amounts of this vitamin because they are pregnant or have certain diseases. Vitamin B12 is in a class of medications called vitamins. It enters the bloodstream through the nose, so it can be used to supply vitamin B12 to people who cannot take in this vitamin through the intestine.

How should this medicine be used?

Vitamin B12 (Cyanocobalamin nasal gel) comes as a gel to apply to the inside of the nose. It is usually used once a week. To help you remember to use Vitamin B12, use it on the same day of the week every week. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Use Vitamin B12 exactly as directed. Do not use more or less of it or use it more often than prescribed by your doctor.

Vitamin B12 will supply you with enough vitamin B12 only as long as you use it regularly. You may need to use Vitamin B12 every week for the rest of your life. Continue to use Vitamin B12 even if you feel well. Do not stop using Vitamin B12 without talking to your doctor. If you stop using Vitamin B12, your anemia may return and your nerves may be damaged.

Hot foods and drinks may cause your nose to produce mucus that can wash away Vitamin B12. Do not eat or drink hot foods or drinks for 1 hour before you plan to use Vitamin B12 or for 1 hour after you use this medication.

Your doctor or pharmacist will show you how to use Vitamin B12. You will also be given the manufacturer’s printed information on using this medication. Read the information carefully and ask your doctor or pharmacist if you have any questions.

To use the nasal gel, follow these steps:

  1. Blow your nose gently to clear both nostrils.
  2. Pull the clear cover off of the top of the pump.
  3. If you are using the pump for the first time, press down on the finger grips of the pump firmly and quickly until you see a droplet of gel at the top of the pump. Then press down on the finger grips two more times.
  4. Place the tip of the pump about halfway into one nostril. Be sure to point the tip toward the back of your nose.
  5. Hold the pump in place with one hand. Press your other nostril closed with the forefinger of your other hand.
  6. Press down firmly and quickly on the finger grips to release medication into your nostril.
  7. Remove the pump from your nose.
  8. Massage the nostril where you applied the medication for a few seconds.
  9. Wipe the tip of the pump with a clean cloth or an alcohol swab and replace the clear cap on the tip of the pump.

Other uses for this medicine

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What special precautions should I follow?

Before using Vitamin B12 ,

  • tell your doctor and pharmacist if you are allergic to Vitamin B12, tablets, or injection; hydroxycobalamin; multi-vitamins; any other medications or vitamins; or cobalt.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking. Be sure to mention any of the following: azathioprine; antibiotics such as chloramphenicol; cancer chemotherapy; colchicine; folic acid; iron supplements; medications for human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) such as lamivudine (Epivir) and zidovudine (Retrovir); methotrexate (Rheumatrex, Trexall), para-aminosalicylic acid (Paser), and pyrimethamine (Daraprim). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you drink or have ever drunk large amounts of alcohol, if you have any type of infection, and if you have or have ever had Leber’s hereditary optic neuropathy (slow, painless loss of vision, first in one eye and then in the other); allergies that often cause your nose to be stuffed, itchy, or runny; or kidney disease.
  • tell your doctor if you get a cold or a runny or stuffy nose at any time during your treatment. You may have to use another form of vitamin B12until your symptoms go away.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while using Vitamin B12, call your doctor. Talk to your doctor about the amount of vitamin B12you should get every day when you are pregnant or breastfeeding.

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do if I forget a dose?

Use the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not use a double dose to make up for a missed one.

What side effects can this medication cause?

Vitamin B12 may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • headache
  • upset stomach
  • stuffed or runny nose
  • sore tongue
  • weakness

Some side effects can be serious. The following symptoms are uncommon, but if you experience any of them, call your doctor immediately:

  • unusual bruising or bleeding
  • muscle weakness, cramps, or pain
  • leg pain
  • extreme thirst
  • frequent urination
  • confusion
  • burning or tingling in the arms, legs, hands or feet
  • sore throat, fever, chills, or other signs of infection
  • rash
  • hives
  • itching
  • difficulty breathing or swallowing

Vitamin B12 may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online ( or by phone (1-800-332-1088).

What should I know about storage and disposal of this medication?

Keep this medication upright in the carton it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Do not allow the medication to freeze.

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website ( for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach.

In case of emergency/overdose

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

What other information should I know?

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body’s response to Vitamin B12.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

Brand names

  • Nascobal®

Other names

  • Vitamin B12

Disclaimer: DrLinex has made every effort to ensure that all information is factually accurate, comprehensive and up-to-date. However, this article should not be used as a licensed health care professional’s choice of knowledge and expertise. You should always consult your doctor or other health care professional before taking any medication. The information given here is subject to change and it has not been used to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions or adverse effects. The lack of warning or other information for any drug does not indicate that the combination of medicine or medication is safe, effective or appropriate for all patients or all specific uses.

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