SeriousTiming Sensitive
Calcium
Calcium can reduce oral Tetracycline absorption when taken together.
Recommendation: Separate tetracycline from calcium supplements and dairy-heavy supplement doses by several hours.
Tetracycline
Prescription ·Strong evidence ·Reviewed May 2026
Tetracycline is a broad-spectrum, bacteriostatic antibiotic of the tetracycline class used to treat a range of bacterial infections and inflammatory acne vulgaris. It is active against many gram-positive and gram-negative organisms as well as atypical pathogens such as Mycoplasma, Chlamydia, and Rickettsia. Its absorption is markedly reduced by chelation with divalent and trivalent cations found in dairy products, antacids, and mineral supplements.
What it's good for
- Inflammatory acne vulgaris1
- Respiratory tract infections (e.g., those caused by Mycoplasma pneumoniae)
- Rickettsial infections (e.g., Rocky Mountain spotted fever, typhus)
- Chlamydial infections (e.g., trachoma, urethritis)
- Helicobacter pylori eradication (as part of combination therapy)
What to watch for
- Gastrointestinal upset (nausea, vomiting, diarrhea, epigastric burning)
- Photosensitivity (exaggerated sunburn reaction)
- Permanent tooth discoloration when used in children under 8 years or during tooth development
- Known hypersensitivity to tetracyclines1,2
- Pregnancy (risk of fetal harm and maternal hepatotoxicity)
The bottom line
Evidence rating strong. Most-documented uses: inflammatory acne vulgaris, respiratory tract infections (e.g., those caused by mycoplasma pneumoniae), rickettsial infections (e.g., rocky mountain spotted fever, typhus). 3 sources indexed (1985–2012), with 5 interaction records on file.
The science
How it works, mechanistically.
Core mechanism
Tetracycline inhibits bacterial protein synthesis by reversibly binding to the 30S ribosomal subunit, where it blocks the attachment of aminoacyl-tRNA to the acceptor (A) site of the mRNA-ribosome complex. This prevents addition of new amino acids to the growing peptide chain, halting bacterial growth (a bacteriostatic effect). The drug enters bacterial cells partly by passive diffusion and partly by an energy-dependent active transport system that concentrates it intracellularly, accounting for its selectivity for bacterial over mammalian ribosomes. In acne, additional anti-inflammatory effects and suppression of Cutibacterium acnes contribute to clinical benefit.2,1
Class
Tetracycline antibiotic
Absorption
Best on an empty stomach
Dosing
Dosing & protocol.
Common range
Adults: 250-500 mg orally every 6 hours (1-2 g/day); for acne, lower maintenance doses such as 250-500 mg once or twice daily are common
Recommended form
Oral capsule or tablet taken on an empty stomach (1 hour before or 2 hours after meals)
Absorption is significantly impaired by food, milk and other dairy products, and by divalent/trivalent cations including calcium, magnesium, iron, zinc, and aluminum (found in antacids and supplements) due to chelation. Take on an empty stomach, at least 1 hour before or 2 hours after meals, and separate from dairy, antacids, and mineral supplements by 2-3 hours.
Depletions
What it depletes.
Nutrients this medication can lower over time, and what to replace.
Calcium
MildTetracycline chelates divalent and trivalent cations, forming insoluble, poorly absorbed complexes with calcium in the gut. Concurrent intake (especially with dairy) markedly reduces absorption of both the drug and dietary calcium; long-term use may modestly affect calcium status.
Replace Calcium citrateMonitor Serum calcium (ionized or albumin-corrected)Onset Acute reduction in absorption with each co-administered dose; clinically meaningful status effects only with prolonged use over weeks to months
Iron
MildTetracycline and iron form mutual chelation complexes in the gastrointestinal tract, impairing absorption of both. Co-administration significantly lowers serum iron uptake and reduces tetracycline bioavailability.
Replace Ferrous sulfate (taken at least 2-3 hours apart from the drug)Monitor Serum ferritin and transferrin saturationOnset Per-dose impairment of iron absorption when taken together; relevant to iron status only with concurrent prolonged use or pre-existing deficiency
Magnesium
MildAs a divalent cation, magnesium forms insoluble chelates with tetracycline in the gut, reducing absorption of both agents. Antacids and supplements containing magnesium are a recognized cause of this interaction.
Replace Magnesium glycinate (separated from the drug by 2-3 hours)Monitor Serum magnesiumOnset Acute, dose-by-dose reduction in absorption when co-ingested; minimal systemic depletion otherwise
Zinc
MildZinc, a divalent cation, chelates with tetracycline to form complexes that are poorly absorbed, lowering bioavailability of both the antibiotic and zinc when taken concurrently.
Replace Zinc gluconate (taken several hours apart from the drug)Monitor Plasma or serum zincOnset Per-dose absorption interference; clinically significant zinc status changes are uncommon with short courses
Safety
Full safety detail.
Side effects
- Gastrointestinal upset (nausea, vomiting, diarrhea, epigastric burning)
- Photosensitivity (exaggerated sunburn reaction)
- Permanent tooth discoloration when used in children under 8 years or during tooth development
- Esophageal irritation or ulceration if taken with insufficient water or before lying down
- Candidal overgrowth (oral thrush, vaginal candidiasis)
- Hepatotoxicity (especially with high doses or in pregnancy)
- Pseudotumor cerebri (benign intracranial hypertension)
- Hypersensitivity reactions and rash
Contraindications
- Known hypersensitivity to tetracyclines1,2
- Pregnancy (risk of fetal harm and maternal hepatotoxicity)
- Breastfeeding
- Children under 8 years of age (risk of permanent tooth staining and effects on bone growth)
- Use of outdated or degraded tetracycline (risk of Fanconi-like syndrome)1,2
- Concurrent use with isotretinoin or other systemic retinoids (increased risk of pseudotumor cerebri)
Interactions
Interaction records.
SeriousTiming Sensitive
Iron
Iron can reduce oral Tetracycline absorption when taken together.
Recommendation: Separate tetracycline from iron supplements by several hours.
SeriousTiming Sensitive
Magnesium Glycinate
Magnesium Glycinate can reduce oral Tetracycline absorption when taken together.
Recommendation: Separate tetracycline from magnesium supplements, antacids, and mineral products by several hours.
SeriousTiming Sensitive
Zinc
Zinc can reduce oral Tetracycline absorption when taken together.
Recommendation: Separate tetracycline from zinc supplements by several hours.
InfoTiming Sensitive
Probiotics
Tetracycline is a broad-spectrum antibiotic that can kill the live bacteria in probiotic supplements taken at the same time, reducing the viability and intended benefit of the probiotic. Probiotics are commonly used to mitigate antibiotic-associated gastrointestinal upset.
Recommendation: Separate the probiotic from the antibiotic dose by at least 2 hours to preserve probiotic viability. Continuing a probiotic during and after the antibiotic course may help reduce antibiotic-associated diarrhea.
Sources
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Meta-analyses & systematic reviews
1- 1Antibiotics for acne vulgaris (systematic review)Needs reviewNo linkCochrane Skin Group · Cochrane Database of Systematic Reviews · 2012
Oral tetracycline-class antibiotics reduce inflammatory acne lesions and are a standard treatment for moderate inflammatory acne.
Reviews & position papers
2- 2Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistanceNeeds reviewPMIDChopra I, Roberts M · Microbiology and Molecular Biology Reviews · 2001
Tetracyclines reversibly bind the 30S ribosomal subunit and block aminoacyl-tRNA binding to the A site, producing a bacteriostatic effect across a broad range of bacteria.
- 3Influence of food and milk on the absorption of tetracyclineNeeds reviewNo linkVarious · Clinical Pharmacology and Therapeutics · 1985
Co-administration with milk, food, or polyvalent cation-containing products markedly reduces tetracycline bioavailability owing to chelation, supporting empty-stomach dosing.
Keep exploring
Deep dives & adjacent profiles.
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
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