| Document And Entity Information | Oct. 12, 2021 |
| Document Information [Line Items] | |
| Entity, Registrant Name | BIOCARDIA, INC. |
| Document, Type | 8-K |
| Document, Period End Date | Oct. 12, 2021 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 0-21419 |
| Entity, Tax Identification Number | 23-2753988 |
| Entity, Address, Address Line One | 125 Shoreway Road, Suite B |
| Entity, Address, City or Town | San Carlos |
| Entity, Address, State or Province | CA |
| Entity, Address, Postal Zip Code | 94070 |
| City Area Code | 650 |
| Local Phone Number | 226-0120 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000925741 |
| CommonStockParValue0001 Custom [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $0.001 |
| Trading Symbol | BCDA |
| Security Exchange Name | NASDAQ |
| WarrantToPurchaseCommonStock Custom [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrant to Purchase Common Stock |
| Trading Symbol | BCDAW |
| Security Exchange Name | NASDAQ |
