Hello
@SHmano Insulin sensitivity can change for many reasons, heat, exercise, weight changes, hormones, stress. There isn't a specific answer to your question, what's vital is if your insulin needs are changing then keep a diary/log, and record doses, food/carbs eaten, review your ratios regularly.
Also have you ever done any basal testing to check your Insulatard dose is right for your daily needs ? I'd do a check on this as getting the basal insulin right is essential for good control.