Antibiotics (Broad-Spectrum)
Common brand names: Amoxicillin, Doxycycline, Azithromycin
Three nutrients listed against this medication. The most severe is marked critical.
At a glance
One of the three is marked well documented. The other two carry their own evidence levels.
At a glance
- Probiotics / Gut MicrobiomeCritical · Well documented
- Vitamin K2Moderate · Moderate evidence
- B Vitamins (Biotin, B complex)Mild · Mechanism only, no human trial
Color shows how serious each listed effect is. The label beside it shows how strong the evidence is. The cards below explain each one and show its evidence.
Nutrients it can lower
Mechanism, Broad-spectrum antibiotics eliminate both pathogenic AND beneficial bacteria. A single course can markedly reduce gut microbiome diversity, with some species not recovering for months. Background figure, not from a trial cited on this record.
Common signs, Diarrhea, bloating, increased infection susceptibility, immune dysregulation, C. diff risk
Dethlefsen et al. (PLoS Biol, 2008; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 19018661): a course of ciprofloxacin produced pervasive, in part incompletely reversible shifts in the human gut microbiota (deep 16S sequencing).
A multi-strain probiotic (10–50 billion CFU) was used during and for 2 weeks after antibiotics. Saccharomyces boulardii specifically reduces C. diff risk. Separating the probiotic from the antibiotic dose by about 2 hours is standard pharmacy guidance rather than a parameter tested in the cited trial.
Mechanism, Gut bacteria are a significant source of Vitamin K2 (menaquinones). Antibiotic courses reduce K2 production. Relevant especially for those on warfarin.
Common signs, Impaired arterial calcium regulation, bone health impairment
Conly & Stein (Clin Invest Med, 1994): reduction in gut menaquinone (vitamin K2) production during antibiotic therapy.
Vitamin K2 (MK-7) 100 mcg daily after a course is a figure in common use, not from a trial cited on this row. The cited paper measured reduced vitamin K2 in human liver during broad-spectrum antimicrobial use and tested no supplement.
Mechanism, Gut bacteria synthesize several B vitamins, including biotin and B12, and broad-spectrum antibiotics reduce that bacterial population. Whether the loss of this endogenous source is large enough to move a person's B-vitamin status has not been quantified in a human trial.
Common signs, Fatigue, hair loss (biotin), neurological symptoms
Gut bacteria synthesize biotin and other B vitamins; broad-spectrum antibiotics can reduce this source (physiology review, Said, 2011). No human trial quantifies a resulting deficiency.
B-complex supplement during and 2 weeks after antibiotic course.
For your next appointment
It prints or saves as a single page. Whether to add a supplement for a nutrient this medication may lower is a decision for your prescriber.
Disclosure
These statements have not been evaluated by the Food and Drug Administration. Any grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →