Vitamin b12 and Synthroid drug interactions - from FDA reports


Drug interactions are reported among people who take Vitamin b12 and Synthroid together. This study is created by eHealthMe based on reports of 4,281 people who take Vitamin b12 and Synthroid from FDA, and is updated regularly.

What's eHealthMe?

eHealthMe is a health data analysis company based in Mountain View, California. eHealthMe monitors and analyzes the outcomes of drugs and supplements that are currently on the market. The results are readily available to health care professionals and consumers.

eHealthMe has released original studies on market drugs and worked with leading universities and institutions such as IBM, London Health Science Centre, Mayo Clinic, Northwestern University and VA. eHealthMe studies have now been referenced in over 500 peer-reviewed medical publications.

How we gather our data?

Healthcare data is obtained from a number of sources including the Food and Drug Administration (FDA). This information is aggregated and used to produce personalized reports that patients can reference.

The information that eHealthMe collects includes:

  • Side effects (including severity and how people recover from them)
  • Associated conditions or symptoms
  • Drug effectiveness
  • Demographic data regarding drug use

How the study uses the data?

The study is based on cobalamin and levothyroxine sodium (the active ingredients of Vitamin b12 and Synthroid, respectively), and Vitamin b12 and Synthroid (the brand names). Other drugs that have the same active ingredients (e.g. generic drugs) are not considered.

What is Vitamin b12?

Vitamin b12 has active ingredients of cobalamin. It is often used in vitamin b12 deficiency. (latest outcomes from Vitamin b12 52,249 users)

What is Synthroid?

Synthroid has active ingredients of levothyroxine sodium. It is often used in hypothyroidism. (latest outcomes from Synthroid 170,727 users)

How to use the study?

Patients can bring a copy of the report to their healthcare provider to ensure that all drug risks and benefits are fully discussed and understood. It is recommended that patients use the information presented as a part of a broader decision-making process.

On Feb, 18, 2019

4,281 people who take Vitamin b12, Synthroid are studied.

Number of reports submitted per year:

Vitamin b12 and Synthroid drug interactions.

Most common drug interactions over time *:

< 1 month:
  1. Insomnia (sleeplessness)
  2. Nausea (feeling of having an urge to vomit)
  3. Dyspnoea (difficult or laboured respiration)
  4. Aortic stenosis (obstruction to the outflow of blood from the left ventricle into the aorta)
  5. Aspartate aminotransferase increased
  6. Dizziness
  7. Dyspepsia (indigestion)
  8. Face injury
  9. Faecal volume increased
  10. Fall
1 - 6 months:
  1. Abdominal distension
  2. Anxiety
  3. Back pain
  4. Confusional state
  5. Dehydration (dryness resulting from the removal of water)
  6. Immunodeficiency
  7. Neurogenic bladder (the normal function of the bladder is to store and empty urine in a coordinated, controlled fashion)
  8. Opportunistic infection (a microorganism that normally does not cause disease but becomes pathogenic when the body's immune system is impaired and unable to fight)
  9. Oral candidiasis (fungal infection of mouth)
  10. Rash
6 - 12 months:
  1. Fall
  2. Foot fracture
  3. Pregnancy
  4. Respiratory tract infection
  5. Vaginal haemorrhage (vaginal bleeding)
  6. Vaginal infection
  7. Asthenia (weakness)
  8. Condition
  9. Hypotension (abnormally low blood pressure)
  10. Insomnia (sleeplessness)
1 - 2 years:
  1. Nausea (feeling of having an urge to vomit)
  2. Pain in extremity
  3. Drug ineffective
  4. Nephrolithiasis (calculi in the kidneys)
  5. Post-traumatic stress disorder
  6. Depression
  7. Diarrhoea
  8. Malaise (a feeling of general discomfort or uneasiness)
  9. Palpitations (feelings or sensations that your heart is pounding or racing)
  10. Tinnitus (a ringing in the ears)
2 - 5 years:
  1. Chronic kidney disease
  2. Depression
  3. Escherichia bacteraemia (presence of bacteria escherichia coli in the blood)
  4. Fall
  5. Frequent bowel movements
  6. Hypoaesthesia (reduced sense of touch or sensation)
  7. Hypoaesthesia oral (reduced sense of touch or sensation in mouth)
  8. Influenza
  9. Injury
  10. Middle insomnia (difficulty returning to sleep after awakening either in the middle of the night)
5 - 10 years:
  1. Blood pressure decreased
  2. Nephrolithiasis (calculi in the kidneys)
  3. Anxiety
  4. Asthenia (weakness)
  5. Blood pressure increased
  6. Chest pain
  7. Cushing's syndrome (obesity, a rounded face, increased fat)
  8. Deep vein thrombosis (blood clot in a major vein that usually develops in the legs and/or pelvis)
  9. Injury
  10. Metabolic syndrome (a combination of the medical disorders that, when occurring together, increase the risk of developing cardiovascular disease)
10+ years:
  1. Nausea (feeling of having an urge to vomit)
  2. Neuropathy peripheral (surface nerve damage)
  3. Nephropathy (damage to or disease of a kidney)
  4. Oedema (fluid collection in tissue)
  5. Rash
  6. Weight increased
  7. Acute prerenal failure (prerenal acute renal failure (arf) occurs when a sudden reduction in blood flow to the kidney)
  8. Addison's disease (addison's disease, a hormonal disorder disease)
  9. Affective disorder (mental disorder)
  10. Amnesia (deficit in memory caused by brain damage, disease, or psychological trauma)
not specified:
  1. Nausea (feeling of having an urge to vomit)
  2. Diarrhoea
  3. Pain
  4. Drug ineffective
  5. Dyspnoea (difficult or laboured respiration)
  6. Arthralgia (joint pain)
  7. Headache (pain in head)
  8. Asthenia (weakness)
  9. Dizziness
  10. Fall

Most common drug interactions by gender *:

  1. Cough
  2. Dizziness
  3. Fall
  4. Asthenia (weakness)
  5. Malaise (a feeling of general discomfort or uneasiness)
  6. Weight decreased
  7. Pain in extremity
  8. Vomiting
  9. Nasopharyngitis (inflammation of the nasopharynx)
  10. Gait disturbance
  1. Diarrhoea
  2. Nausea (feeling of having an urge to vomit)
  3. Fall
  4. Pyrexia (fever)
  5. Pneumonia
  6. Arthralgia (joint pain)
  7. Blood pressure increased
  8. Malaise (a feeling of general discomfort or uneasiness)
  9. Haemoglobin decreased
  10. Weight decreased

Most common drug interactions by age *:

  1. Foetal exposure during pregnancy (exposing your unborn child to contraindicated in pregnancy leads birth defect)
  2. Viral infection
  3. Viral rash
  4. Hypoglycaemia (deficiency of glucose in the bloodstream)
  1. Hypotonia (low muscle tone)
  2. Abnormal behaviour
  3. Anxiety
  4. Bruxism (habitual grinding of the teeth, typically during sleep)
  5. Condition
  6. Dermatillomania (skin picking disorders)
  7. Disturbance in attention
  8. Ear infection
  9. Increased appetite
  10. Nail picking
  1. Headache (pain in head)
  2. Abdominal pain upper
  3. Bone pain
  4. Bronchitis (inflammation of the mucous membrane in the bronchial tubes)
  5. Cough
  6. Dry mouth
  7. Dysphonia (speech disorder attributable to a disorder of phonation)
  8. Lymphadenopathy (disease or enlargement of lymph nodes)
  9. Oropharyngeal pain
  10. Pulmonary congestion (congestion in the lungs)
  1. Injection site pain
  2. Anxiety
  3. Rash pruritic (redness with itching)
  4. Depressed level of consciousness
  5. Nausea (feeling of having an urge to vomit)
  6. Polycystic ovaries (cysts in the ovaries that occurs when the follicle stops developing)
  7. Drug ineffective
  8. Bronchitis (inflammation of the mucous membrane in the bronchial tubes)
  9. Condition
  10. Depression
  1. Pain
  2. Headache (pain in head)
  3. Pyrexia (fever)
  4. Nausea (feeling of having an urge to vomit)
  5. Asthenia (weakness)
  6. Dizziness
  7. Diarrhoea
  8. Malaise (a feeling of general discomfort or uneasiness)
  9. Drug ineffective
  10. Weight increased
  1. Nausea (feeling of having an urge to vomit)
  2. Diarrhoea
  3. Dizziness
  4. Pneumonia
  5. Malaise (a feeling of general discomfort or uneasiness)
  6. Weight decreased
  7. Vomiting
  8. Pain in extremity
  9. Back pain
  10. Nasopharyngitis (inflammation of the nasopharynx)

* Approximation only. Some reports may have incomplete information.

Do you take Vitamin b12 and Synthroid?

You are not alone:

Related studies

Browse interactions by gender and age

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Male: 0-1 2-9 10-19 20-29 30-39 40-49 50-59 60+

Interactions between Vitamin b12 and drugs from A to Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
Interactions between Synthroid and drugs from A to Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
Browse all drug interactions of Vitamin b12 and Synthroid
a b c d e f g h i j k l m n o p q r s t u v w x y z

What would happen?

Predict new side effects and undetected conditions when you take Vitamin b12 and Synthroid (58,333 reports studied)

FDA reports used in this study

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WARNING: Please DO NOT STOP MEDICATIONS without first consulting a physician since doing so could be hazardous to your health.

DISCLAIMER: All material available on is for informational purposes only, and is not a substitute for medical advice, diagnosis, or treatment provided by a qualified healthcare provider. All information is observation-only, and has not been supported by scientific studies or clinical trials unless otherwise stated. Different individuals may respond to medication in different ways. Every effort has been made to ensure that all information is accurate, up-to-date, and complete, but no guarantee is made to that effect. The use of the eHealthMe site and its content is at your own risk.

You may report adverse side effects to the FDA at or 1-800-FDA-1088 (1-800-332-1088).

If you use this eHealthMe study on publication, please acknowledge it with a citation: study title, URL, accessed date.

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