Medications Urgent might be a metacam overdose

We can't tell anything about whether she's had too much without knowing the strength of the Metacam. It comes in more than one strength -- the stronger one requires a smaller dose, the weaker one a larger dose.

If she were mine, I'd try to get her up and moving, or at least awake. Movement will speed the metabolism of it, at least a little bit. And keep her warm, but don't let her get overheated.

Metacam does have a range of dosage, and the new guidelines allow for more than the old ones. So I hope your pig will be OK. Do keep us posted on how she's doing.

It I said 0.5mg/ml I think and I'm sorry to say she passed away I tried everything but unfortunately it didn't work. On the box for her body weight she should've had 3 DROPS and the syringe he told me to use was for a 3kg animal instead. I feel so bad for not noticing before I have it to her

Hi khw10,
such a scary thing you're going though. I'm sorry this happening. I hope she gets well soon.

My condolences for your loss.

The vet didn't make a mistake, the dosage prescribe was correct if that is the right concentration. Guinea pigs are often dosed with Meloxicam (Metacam) at a rate of 0.2mg per 1 kg of body weight once every 24 hours for pain management (I have seen much lower doses prescribed for reducing inflammation not pain management). See this page for reference to the dosage rates https://www.guinealynx.info/analgesics.html

As she was 800 grams she should have been getting 0.16mg of medication per 24 hours if dosed at 0.2mg per 1 kg. To get her 0.16mg with a liquid suspension containing 0.5mg per mL would need 0.32mL. Here is a calculator you can use if you know the medication concentration and the dosage rate needed https://reference.medscape.com/calculator/weight-dosing

If this is the dose she was given it was not an overdose. You didn't make a mistake in giving it to her. It is very unfortunate that she has passed but I don't think the outcome would have been any different had you not given her the Metacam.

I'm very sorry you lost her.
@Soecara is right about the dose. It doesn't sound as though she had an overdose, and it's unlikely the metacam had anything to do with her death.