How Long Does A B12 Shot Last (And Why)?

Exact Answer: 7 days

There are many factors that would affect the lasting time of Vitamin B12 injection. The lasting time may get affected by the metabolic rate of a person. The body type and health conditions of the person may also influence the lasting time of the Vitamin B12 shot.

The dosage of Vitamin B12 would be different for people depending on their requirements. After the administration of Vitamin B12 shot, the body would absorb it within a few minutes. This is why many people choose B12 injection over chewable tablets. Sometimes, the injection effects would not stay for more than 24 to 48 hours.

Some people may see the elimination of the B12 shot just after 8 hours of the administration.

How Long Does A B12 Shot Last?

B12 ShotTime
In days7 days
In hours168 hours

The half-life of the B12 shot would be around 6 days in some people according to experts. The effects of B12 would be seen by the person for a week if the solution stays inside the body for around 6 days. The solution would be excreted from the body after a few days. People can use B12 shots for helping nerve function.

People can also use the B12 shot for creating red blood cells. People who are low on energy can get the B12 injection for increasing their energy level. The people who require immediate effects of Vitamin B12 should try to take the injection after the doctor’s recommendation.

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After administration, the injection would start spreading in the whole body within a few minutes. After uniform distribution of the Vitamin B12 solution, the liver would store the extra solution, as the liver plays the role of primary storage for vitamins. Nobody should take an overdose of vitamin B12 shots.

Everyone should repeat the B12 shot every 10 days. People should follow the repetition dose of B12 according to the suggestion of the doctor. The deficiency level of Vitamin B12 would also affect the lasting time of the B12 shot.

People who have a very low level of B12 would require the dose very as the effects would not stay for more than 24 to 36 hours. The doctor should try to get a body check-up to know the body’s nutritional requirements.

Why Does A B12 Shot Last This Long?

Vitamin B12 is water-soluble which would get eliminated from the body in a few hours or days. People who have severe kidney problems may see the toxicity of vitamin B12 injections if taken in high amounts, as the excess vitamin B12 won’t get eliminated from the body easily.

After the administration of the injection, nobody should put any excess strain on the body. The results of vitamin B12 would be seen by the person after 1 to 3 days of administration. The person can see many benefits if the shot is taken for around 2 to 3 months as prescribed by the doctor.

Depending on the requirement and purpose, the lasting time of vitamin B12 shots would vary. Nobody should try to inject the vitamin B12 solution on their own. An expert or professional help should be taken for taking the vitamin B12 shot. Everybody should try to maintain a good lifestyle to avoid the side effects of a vitamin B12 shot.

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People should avoid drinking excess alcohol if they have taken the vitamin B12 shot. If anybody sees no change in the health condition after 2 to 3 days of administration of B12. Then the person should inform the doctor or professional about the same. The doctor may increase the dosage or tell why the injection is not showing any effects.


The lasting time of vitamin B12 injection would be around 5 to 7 days. The person’s requirement and nutritional factors would influence the lasting time of vitamin B12. Everyone needs to get a body check-up done to know, how much vitamin B12 is required. The person should avoid eating unhealthy food to make vitamin B12 work faster.

To get too many benefits from the vitamin B12 shot, everyone should consult their doctor for better suggestions. Everyone should talk to the doctor for knowing the best form of vitamin B12 for themselves.



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Hi! I'm Nidhi.

Here at the EHL, it's all about delicious, easy recipes for casual entertaining. So come and join me at the beach, relax and enjoy the food.

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