Thyronorm, diarrhoea and syringes

[MabelMarple]

My cat started on thyronorm two weeks ago.
Noticeable improvement in behaviour already. He's eating well but no longer frantic for food.
I have struggled with the syringe and can't find the answer on google so just wondered if anyone could help. The plunger has a stopper with a pointy bit on the end. I've been pulling it until the stopper reaches the 2.5 line. Is this correct or should I be pulling it back to the very tip of the syringe?

Secondly he's had some diarrhoea. He's an outdoor cat but has come home 2 or 3 times with poo all over his tail. Some is dried in and he seems unable to clean it, or he's leaving a trail.... I've tried a warm damp cloth but he's going to maim me if I do more.

I will speak to vet next week in case the dose needs changing.

The correct level is the stopper not the pointy bit.
Diarrhoea is not a common side effect of thyronorm - it is more a symptom of hyperthyroidism. So yes I would talk to your vet.
You should be having a blood test 3-4 weeks after starting the thyronorm to check the thyroid levels, kidney values and red and white cells to make sure the dose is right, that there is no renal unmasking ( hidden kidney disease) or side effects.

Thank you, I have been doing it correctly then.
Vet told me to look out for diarrhoea so I assumed that was a side effect as he hasn't had it before (except for odd occasions when I presume he ate something disgusting).
He's booked in for follow up bloods etc. Unfortunately it's a rural vet only open Wed to Friday so I'll ring then.