Do Kelvin values use a degree symbol?

No. Write kelvin as K (for example 298.15 K), not °K.

Celsius to Kelvin Converter – Convert °C to K

Kelvin and Celsius share the same degree size. Add 273.15: K = °C + 273.15. Absolute zero is 0 K (−273.15°C).

What is 0°C in Kelvin?: 0°C = 273.15 K.
Do Kelvin values use a degree symbol?: No. Write kelvin as K (for example 298.15 K), not °K.