What the FDA labels say about taking them together
Ascorbic acid and doxycycline
Ascorbic acid's FDA label of May 29, 2026 names doxycycline in its drug interactions section; the doxycycline labels PlainMeds reads (4) do not name ascorbic acid. The ascorbic acid label: “DRUG INTERACTIONS Antibiotics: Ascorbic acid may decrease the activities of erythromycin, kanamycin, streptomycin, doxycycline, and lincomycin.”
Check it at the source: the ascorbic acid FDA label on DailyMed (effective May 29, 2026, McGuff Pharmaceuticals, Inc.); the doxycycline FDA label on DailyMed (effective July 25, 2025, Chartwell RX, LLC.).
What does the ascorbic acid label say about doxycycline?
Ascorbic acid label, drug interactionsDRUG INTERACTIONS Antibiotics: Ascorbic acid may decrease the activities of erythromycin, kanamycin, streptomycin, doxycycline, and lincomycin.
Source: FDA drug label (Ascor), McGuff Pharmaceuticals, Inc., effective May 29, 2026 (SPL set 388aad52-fc01-4784-9791-1dbc80c69306), via openFDA; the full label on DailyMed
What does the doxycycline label say about ascorbic acid?
Doxycycline's label (effective July 25, 2025) and its 3 other brand-application labels do not name ascorbic acid in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Doxycycline Monohydrate), Chartwell RX, LLC., effective July 25, 2025 (SPL set 02aa8731-d40f-43d8-8b63-a79a0503f8db), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Ascorbic acid | Doxycycline | |
|---|---|---|
| Labeled for | n/a | Urinary tract infections, Bacterial infections, Acne |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.118 per tablet 100 mg tablet |
| Shortage now | No current entry | A presentation being discontinued |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once