Home > If you are hypothyroid > If you have been diagnosed with hypothyroidism

If you have been diagnosed with hypothyroidism

Once you are diagnosed with hypothyroidism (underactive thyroid), your doctor will start you on levothyroxine, a synthetic form of the thyroid hormone, thyroxine . The starting dose is usually 25mcg or 50mcg.  You will, in most cases, have to take the medication for the rest of your life as it is very rare for people to cease this medication.

You will probably be told to be tested again in two or three months’ time and then make another appointment to see your doctor. Your doctor will then look at your test results, discuss your symptoms with you again, especially any improvement, and then make a decision as to whether or not to increase or decrease your dosage.

When will you see an improvement in symptoms?

You will need to be patient as it can take a long time to improve.  It takes about 7-10 days for the levothyroxine to enter the body’s cells properly so don’t expect any improvement before then.  Some people do see improvement in two weeks but for many, it can take several weeks and even then, only some of the symptoms will improve in the beginning. If you have been ill for a very long time, it can take many months before you are back to normal.

You may find that you have some good days and then some bad days again. At the beginning of treatment, if you feel well one day and do too much, you may well go backwards for a few days.

You need to be careful not to overdo it until you have found the right level for you (your ‘setpoint’).  Remember your body needs to repair itself as well as have enough energy for day to day living so be gentle with yourself and don’t try to do too much too soon.  Don’t try to spring clean the house just because you wake up one morning feeling better or you may regress.

Don’t expect to be well overnight; it just won’t happen. Some symptoms can take as long as 12 -18 months to subside.  Do be patient and you will get well much quicker.

How to take your levothyroxine

There are many things that can interfere with levothyroxine so you need to make sure you take it correctly:

  • take your levothyroxine with water, on an empty stomach.  Wait for at least 30 minutes before you eat
  • do not drink coffee with your levothyroxine as this affects absorption. it’s probably best to wait at least an hour before you drink coffee
  • do not take calcium carbonate (found in calcium and other supplements and antacids) within four hours of your levothyroxine as this affects absorption
  • do not take iron supplements within two hours of your levothyroxine as this affects absorption

What you should do if you forget your thyroid medication

Try to remember to take your medication. It’s difficult at first but you will soon get used to taking medication every day. If you do forget, DO NOT take two day’s medication together – just carry on as normal.  You may find if you have missed more than one day that you notice a recurrence of some of the symptoms you had before.

If you struggle to remember, try purchasing a weekly pill container from your local pharmacy or online. There are lots to choose from to suit your needs.

Do you still feel ill once your levels are within range?

If you still feel ill even though your TSH levels are within range this could be for various reasons.

Some people do not feel well on a particular brand of levothyroxine.  All levothyroxine drugs in the UK are generics (copies) of the original brands.

Some people feel better on one generic than they do on another.  Try to work out if you feel better on a particular generic and ensure that this is the brand given to you by the pharmacy.  If one particular pharmacy does not have it in stock, try another pharmacy.  Pharmacies may be purchasing whatever is cheapest at the time of ordering so you may need to insist on health grounds.  You can try asking your GP to put the name of the generic onto your prescription rather than just “levothyroxine”.

Levothyroxine often contains lactose or may contain mannitol instead of lactose. Some people have lactose intolerance and some people may have an intolerance to mannitol.  Thyroid UK has a list of all thyroid hormone medications in the UK and some non-UK brands including their ingredients.

If you are intolerant to any of the non-active ingredients in a particular generic of levothyroxine, you can ask to have a special medication without these in the ingredients.  These will possibly be more expensive but if you are intolerant or allergic your doctor can prescribe these on a named patient basis.

Are you on enough levothyroxine?

You may not actually be on enough levothyroxine.  Dr Anthony Toft answered questions in the doctors’ magazine, Pulse, in an article entitled, “Key questions on thyroid disease” in which he stated:  

The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range – 0.2-0.5mU/l.

In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.

But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.

This ‘exogenous subclinical hyperthyroidism ’ is not dangerous as long as serum T3 is unequivocally normal.”

Dr Anthony Toft PRCPE CBE LVO

The evidence in regard to a suppressed or low TSH is inconclusive . Some research shows that it may be safe for patients taking long-term thyroxine replacement therapy to have a low but not suppressed TSH level. This is the reason that NICE did not quote actual figures for TSH levels in respect of maintaining levels of TSH in their guidance, “Thyroid disease: assessment and management“. They simply quoted, “Aim to maintain TSH levels within the reference range when treating primary hypothyroidism with levothyroxine. If symptoms persist, consider adjusting the dose of levothyroxine further to achieve optimal wellbeing, but avoid using doses that cause TSH suppression or thyrotoxicosis .”

Professor Graham Leese presented new data at the Annual Society for Endocrinology BES 2010 in Manchester. The patients who took part in the study who had very high (more than 4.0mU/l) or suppressed (less than 0.03mU/l) TSH levels more frequently suffered from heart disease, abnormal heartbeat patterns and bone fractures compared to patients with TSH levels in the normal range (0.4-4.0). Patients who had a slightly low TSH level (0.04 – 0.4mU/l) did not have an increased risk of contracting any of these conditions.1

If your TSH is not near the bottom of the range and you still have symptoms, try taking details of this study to your next appointment with your doctor and discuss the possibility of a further increase of levothyroxine. If you experience signs of over-replacement such as feeling very hot and sweaty, have a tremor and fast heartbeat, you should contact your doctor as soon as possible to discuss going back to your previous dosage.

Most doctors will only do a TSH test once patients are on levothyroxine but it would be better if further tests are done i.e. FT4 and FT3 as this will show if you have enough thyroxine in your body or whether you are converting your levothyroxine to the active hormone, tri-iodothyronine (T3).

Do you convert your thyroxine properly?

 Some people do not convert their thyroxine adequately into the active hormone, T3. This could be due to lack of certain vitamins and minerals especially selenium. Make sure, though, that you have optimum levels of all vitamins and minerals to help your thyroid system run smoothly.

Lack of conversion can also possibly be due to a genetic polymorphism (also called a variant gene that is different to what most people have – usually a small alteration) – the DIO2 gene.

If you want to find out if you have low levels of T3 or to find out if you have the variant gene, Thyroid UK works with various private testing laboratories where you can purchase a private thyroid test.

If you do have low levels of T3, or do not resolve all of your symptoms on levothyroxine, you should discuss with your doctor the possibility of a referral to a thyroid specialist endocrinologist for a trial of liothyronine. The latest guidance from NHS England state that liothyronine can only be initiated by an endocrinologist so you will need a referral.

It is extremely difficult to get liothyronine on the NHS now due to the very high cost. However, brands from outside of the UK are cheaper. You may be able to obtain an NHS prescription for a non-UK brand because they are cheaper, on a “named patient” basis.

Alternatively, if you can get a private prescription you can purchase liothyronine from Europe.

Read about our T3 Campaign and the work we are doing to try and change the situation.

Natural Desiccated Thyroid (NDT)

Some people feel better taking natural desiccated thyroid (NDT). This is what was used before synthetic levothyroxine came on the market.  It is available on the NHS on a normal prescription on a “named patient” basis but recent guidance does not recommend its use.

You may be able to get a trial of this via a private doctor. Thyroid UK has a list of private doctors and practitioners that may be helpful.


You will need to be tested on an annual basis to ensure that your levels are ok.  Remember that there are certain things that can reduce the absorption of your medication.

Also, remember that you need to ensure that your vitamin and mineral status is optimal.

If you have Hashimoto’s disease, it’s possible that you will get other autoimmune diseases such as pernicious anaemia diabetes, lupus etc. If you suddenly start to get new symptoms, ask your doctor to test for these conditions.

Once you are on the right medication for you, the correct dosage for you, you make sure that you take your medication correctly and make sure that you are aware of the other things you should not take near your levothyroxine, you should see a great improvement in your health.

For more support check out our online community:


Date updated: 08/04/21 (V1.6)
Review date:  17/04/22


Is it safe for patients taking thyroxine to have a low but not suppressed serum TSH concentration? Graham Leese & Robert Flynn
Endocrine Abstracts (2010) 21 OC5.6

How useful was this page?

Tap on a star to rate it!

Average rating 4.6 / 5. Vote count: 190

No votes so far! Be the first to rate this page.

We rely on donations so that we can continue to support and campaign for people with thyroid and related conditions.  If you have found our information helpful, please make a donation or become a member.