My 6 yr old dog is very lethargic, not eating or drinking

Without further information it is difficult for me to provide the best advice, though I will certainly try. Please respond when you can and we can continue the chat.

Lethargy, a reduced appetite and lameness can have many causes including:

• Spinal or pelvic disease. Dogs won't often let us know when in pain by whining and usually, the only clue is a reluctance to move. We would consider e.g. a slipped disc or hip arthritis.
• Toxin ingestion e.g. anti freeze, human medicine, a cleaning product, nicotine.
• A stroke / vascular incident.
• Exacerbated arthritis, which has become worse due to an injury or the cold weather

A vet visit would be wise so he can be examined and as we may need to e.g. run some blood tests or take an x-ray.

I suspect he will benefit from some medicine such as pain relief and anti inflammatories.

Try to tempt him with warm and tasty food such as chicken.

If his gums are pale or dry, he has a bloated abdomen or fast breathing, he is becoming more lethargic or you feel he is really not right, he should be seen by an emergency vet tonight.