Blood test timing when insulin dependent

[LynetteP]

I have been underactive ever since RAI over thirty years ago. Unfortunately, due to poor management of thyroxine dosage (consultant didn't know what he was doing and left me to GP) I gained a lot of weight which just wouldn't shift. So I was diagnosed with type 2 diabetes and was prescribed Metformin initially followed over time by every possible oral drug. So now I inject a small dose of insulin daily which hopefully will not interact with thyroxine.

Ever since I found Thyroid Uk I have followed guidelines for when and how to manage blood tests but now I have to inject in the morning followed by breakfast. I'd be grateful for advice how to manage this - do I do injection and breakfast followed by blood test at 9am followed by thyroid meds? 9am is the earliest I can get the test done as, like many other areas, pathology won't do full thyroid tests for GPs so it's a trip o the hospital. Thanks.

[Judithdalston]

I have Hashi and insulin dependent: ideally take any thyroid blood test on empty stomach 8.30- 9am, and 24 hrs since last levo, or 8-12 hrs after last T3 dose. You don’t say what type of insulin you take eg one long acting dose every 24 hours or short acting with food. I presume the former so you could do this anytime as it’s not related to food. Soon as you have had the blood draw take your T3/4 ( I have even taken them to the surgery) with water, and allow a minimum of 30 mins ( 45-60 mins better) before you then eat breakfast. I do intermittent fasting up to 3-4 pm so never have this problem!

[LynetteP in reply to Judithdalston]

Thanks for your reply. I am very new to taking insulin but was told to do injection immediately before breakfast, around 7am. I am using Humulin I which I believe is classed as intermediate. I take 125gm Levothyroxine and 10mg Liothyronine around 5.30 am which I can be sure is sufficient time before coffee and food. In the past I have made sure I get to hospital well before blood tests open at 9am and take meds and breakfast afterwards. I don't know how or whether taking insulin before blood tests will affect results. Part of the reason I've ended up on insulin is that the majority of type 2 drugs have horrible side effects and react with thyroxine. I am about to have an appointment with a different endo (strike permitting) having requested a transfer. The last endo(?) appointment was a 3 minute telephone call followed by a letter which stated that TSH varied through the day and completely ignored my question about T4 and T3 so I am hoping for better things.

[Judithdalston in reply to LynetteP]

I was on humulin for c.10 years and was never told much about when to take it or with what, but then it’s only in the last few years that any levo.box comes with an advice about taking it 30 mins before breakfast etc. I was never aware of judging the Humulin dosing around breakfast, and never noticed any difference between taking Humulin and breakfast to going 15 months ago to Humulin and intermittent fasting ie no food till 5 hrs or so afterwards. I am now on a real long acting insulin Toujeo, and quick short acting Fiasp to go with food , with a 24 hour continuous blood glucose monitor which produces interesting BG results to play about with! I have never seen, or heard from, an NHS endo either for my diabetes nor hypothyroidism…it’s hard to rely on GPs and surgery nurses who have very limited endo knowledge or experience. Good luck.

[SlowDragon Administrator]

Metformin tends to lower TSH

Even more reason to always get Ft4 and Ft3 tested

Plus vitamin D, folate, ferritin and B12 at least annually

What vitamin supplements are you taking