I was taking 25 units. What dose is that?

Answer

Unanswerable as written. A unit is a volume mark on a syringe, not an amount of drug. You need the concentration.

In more detail

An insulin syringe's units measure hundredths of a milliliter: 100 units is 1 mL. What a given number of units carries depends entirely on the concentration of the product, so the same mark can mean very different amounts. When somebody moves to a labeled product and needs to describe their history, the pharmacist or prescriber who supplied the earlier product is the person who can translate it accurately.

Source

Syringe graduation standard (U-100: 100 units per millilitre).

Educational use only, never medical advice. No doses.