Hello, Thank you for asking at HCM. I do not think the cholesterol levels are related to doxycycline treatment. Sometimes we have high cholesterol even though no family history and having a healthy lifestyle. The cholesterol levels you prescribe are higher than what we would call normal. it would be ideal not to be more than 200 and at least not more than 250. Cholesterol is made of good cholesterol (HDL cholesterol) which we would like to be as high as possible (above 40) and the LDL cholesterol which is the bad cholesterol and this one ideally should be less than 130 and above 190 we might consider treatment. There are many argues if we should treat high cholesterol or not if no other risk factors like: age above 50, diabetes, hypertension, smoking, obesity ect 1. Your cholesterol levels are not connected with doxycycline treatment 2. If you are younger than 50 and do not smoke, no diabetes, no hypertension and not obese than you do not have many risk factors and enough reasons to start to treat hyperlipidemia (high cholesterol). 3. If you do not get treatment at the moment you will need to continue the lifestyle measures you are having (less fat and sugar in diet, plenty of fruit and vegetables, avoid animal fat, exercise regularly, be active, watch your weight, do not smoke or use alcohol) and recheck cholesterol again in 6 months. 4 If you have any of those risks I mentioned you will need to speak with your doctor to calculate your cardiovascular risk and start treatment if he finds it needed. 5. If your cholesterol levels continue to be high even though you are having healthy lifestyle it would be good to check the thyroid function: TSH. Thyroid might effect lipids in our body. Hole this is helpful and answers to your questions Best regards,